You can read about inflections in Nepali at:

• Exploring the Building Blocks: A Simple Guide to Morphemes in Nepali

• Nominal Inflections: The Morphological Adaptations of Nepali Nouns, Pronouns and Adjectives

• Verbal Inflections: The Varied Forms of Nepali Verbs

Derivation in Nepali

Derivation is a process of forming new words from existing roots. In contrast to inflection, which is a process of word formation that maintains the lexical category of the root, derivation can change the lexical category of the root. Derivation in Nepali is a highly productive process. It can be categorized into four types:

• Affixation (सर्ग प्रक्रिया)

• Compounding (समास प्रक्रिया)

• Reduplication (द्वित्य प्रक्रिया)

• Euphonic Combination (सन्धि प्रक्रिया)

Affixation

Affixation is the process of word formation by attaching free morphemes - affixes - to the roots. In Nepali, there are two types of affixes: prefix (उपसर्ग) and suffix (प्रत्यय) and hence, the two type of affixation namely, prefixation and suffixation.

# Suffixation
ईख + आलु = ईखालु
पहाड + इया = पहाडिया
पूर्व + एली = पूर्वेली

# Prefixation
अधि + कृत = अधिकृत
उप + नाम = उपनाम
दुस् + साहस = दुस्साहस

Suffixation

Suffixation is a process of word formation by the addition of bound morpheme to the end of the root. The bound morpheme involved in suffixation is called suffix (प्रत्यय/परसर्ग). On the basis of the root they attach to, there are two types of suffixes in Nepali and they are:

• Primary Suffix (कृत् प्रत्यय)

• Secondary Suffix (तद्वित प्रत्यय)

A primary suffix (कृत् प्रत्यय) is added to the end of a verb root to form a primary derivative word (कृदन्त शब्द). A primary derivative word belongs to noun (नाम), verb (क्रियापद), adjective (विशेषण) or adverb (क्रियाविशेषण).

A secondary suffix (तद्वित प्रत्यय) can be applied to anything but a verb root to form a secondary derivative word (तद्वितान्त शब्द). Such suffixes act on noun, pronoun, adjective, adverb and primary derivative word.

On the basis of their ability to maintain or change the lexical category of the base they get attached to, suffixes in Nepali can be of two types. They are:

• Class Maintaining Suffix

• Class Changing Suffix

A class maintaining suffix maintains the lexical category of the root after suffixation. Some of the class maintaining suffixes in Nepali are given in Table 3.

A class changing suffix changes the lexical category of the root after suffixation. Some of the class maintaining suffixes in Nepali are given in Table 4.

Prefixation

Prefixation is the process of word formation in which a bound morpheme is attached to the beginning of a root. Prefix (उपसर्ग) is the bound morpheme which is involved in the process of prefixation. In Nepali, the process of prefixation produces noun, adjective and adverb only.

Prefixes in Nepali can have various effects in the meaning of the base they get attached to. Some of the possible effects of prefixation on meaning of the root are listed below.

• Express the lack of

• Express too much of

• Express negative meaning of the root

• Add special meaning to

Prefixes in Nepali can be divided into three types and they are:

• Prefixes from Sanskrit (तत्सम उपसर्ग)

• Prefixes from Nepali (तत्भव उपसर्ग)

• Prefixes from other sources (आगन्तुक उपसर्ग)

Prefixes from Sanskrit are the prefixes that are taken from Sanskrit language. Some of such prefixes and their meanings are given in Table 5.

Prefixes from Nepali are the prefixes that are from Nepali language itself. Some of such prefixes and their meanings are given in Table 6.

Prefixes from other sources are the type of prefixes that are taken from sources other than Sanskrit and Nepali. Some of such prefixes and their meanings are given in Table 7.

Compounding

Compounding occurs when two or more words combine to form a new word. In Nepali, there are six types of compounding, all of which are listed below:

• Determinative Compound (तत्पुरुस समास)

• Numeral Compound (द्विगु समास)

• Appositional Compound (कर्मधारय समास)

• Adverbial Compound (अव्य्यीभाव समास)

• Attributive Compound (बहुब्रीहि समास)

• Copulative Compound (द्वन्द्व समास)

Determinative Compounding
कामलाई चोर = कामचोर
जग्गाको धनी = जग्गाधनी
भोकले मरी = भोकमरी
रोगबाट मुक्त = रोगमुक्त

Numeral Compounding
सात कोसीको समूह = सप्तकोसी
पाँचवटा पत्रको समूह = पञ्चपात्रो
चार खण्डको समूह = चौखण्ड

Appositional Compounding
फुफू + दिदी = फुफूदिदी
आमा + छोरी = आमाछोरी 
प्रिय + जन = प्रियजन

Adverbial Compounding
यता + उता = यताउता
ध्यान + पूर्वक = ध्यानपूर्वक
यस + अर्थ = यसर्थ

Attributive Compounding
लामो पात भएको = लमपाते
चारवटा मुख भएको = चौमुखी
लाज नभएको = निर्लज्ज

Copulative Compounding
चाल र चलन = चालचलन 
तल र माथि = तलमाथि 
धन र सम्पत्ति = धनसम्पत्ति

Determinative Compound

A determinative compound is formed when the first word loses its case marker (विभक्ति चिन्ह) when combining with the second root. Such compounds express the meaning of the second root and the meaning of the first word is lost in the process. There are six types of determinative compounds, all of which are listed and described in Table 8.

Numeral Compound

When a numeral adjective (सङ्ख्यावाचक विशेषण) and collective noun (समूहवाचक नाम) combine, a numeral compound is formed. Some of such compounds are given below:

Independent Form => Compound Word
नौ गेडाको समूह => नौगेडी
आठ आनाको समूह => अठन्नी
तीन कोणको समूह => त्रिकोण
सात ऋषिको समूह => सप्तऋषि
नौवटा रात्रिको समूह => नवरात्री

Appositional Compound

An appositional compound is formed when:

• An adjective (विशेषण) combines with an adjective

• A noun (नाम) combines with a noun

• An adjective combines with a noun

• A metaphor (उपमा) combines with a word to be compared (उपमेय)

• An attribute (आरोप) combines with a word to be attributed (आरोप्य)

All the independent words forming an appositional compound have equal importance. Types and example of appositional compounds are given in Table 9.

Adverbial Compound

An adverbial compound is usually an indeclinable word (अव्यय) formed when two indeclinable words or any other words combine. Some of such compounds are listed below:

Independent Form => Compound Word
आज + भोलि => आजभोलि
बिना + पैसा => बिनापैसा
रात + दिन => रातदिन
फल + स्वरूप => फलस्वरूप
यस + कारण => यसकारण

Attributive Compound

An attributive compound is an adjective, which is formed when two or more words combine. An attributive compound expresses a new meaning, which is different from that of the independent words. The types of attributive compound are described in Table 10.

Copulative Compound

Copulative compounds are formed when two or more words connected by a conjunction combine by losing the conjunction. The types of copulative compound are listed in Table 11.

Reduplication

Reduplication (द्वित्व) means repetition. It is a process of word formation in which a root or a part of the root repeats in order to derive a new word. Reduplication can be classified into three distinct types and they are:

• Total Reduplication (पूर्ण द्वित्व)

• Partial Reduplication (आंशिक द्वित्व)

• Echo Reduplication (आपरिवर्तित द्वित्व)

Total Reduplication
बाटो + बाटो = बाटैबाटो
तान + तान = तानातान
तँ + तँ = तँतँ

Partial Reduplication
सम्मान + सम्मान = ससम्मान
झगडा + झगडा = झैझगडा
तयार + तयार = तम्तयार

Echo Reduplication
तेल + तेल = तेलसेल
खटन + खटन = खटनपटन
घर + घर = घरसर

Total Reduplication

New words are formed when an entire word repeats in the process of word formation. Such words express varied levels of intensity to the meaning represented by the root. Some of such compounds are given below:

Independent Form => Compound Word
खल खल => खलखल
खेद खेद => खेदाखेद
तान तान => तानातान

Partial Reduplication

In partial reduplication, only a part of a word is repeated to form a new word. Some of such compounds are given below:

Independent Form => Compound Word
झगडा झगडा => झैझगडा
कसले कसले => क-कसले
सल्लाह सल्लाह => सरसल्लाह

Echo Reduplication

A word formed due to echo reduplication is similar to the one formed due to total reduplication. The only difference is that the initial syllable of the second copy of the root replaced by a similar sounding substring. The process of echo reduplication expresses higher level of intensity to the meaning of the root. Some of such compounds are given below.

Independent Form => Compound Word
केटो केटो => केटोसेटो
नरम नरम => नरमकरम
टाल् टाल् => टालटुल

Euphonic Combination

Euphonic Combination is the joining of two phonemes from two different words to derive a single word. In Nepali, we can find two different categories of the euphonic combination. The first category contains all the types of euphonic combination taken from Sanskrit (तत्सम सन्धि) as Nepali is one of the languages which is derived from Sanskrit. The other category contains the types of euphonic combination specific to Nepali language (तत्भव सन्धि).

Sanskrit Euphonic Combination
उप + अध्यक्ष = उपाध्यक्ष
महा + इन्द्र = महेन्द्र
अधि + आत्मा = अध्यात्म

Nepali Euphonic Combination
मोटा + आइ = मोटाइ 
जाउ + अत = जावत
राती + ओली = रत्यौली

Negation due to Prefixation

Negation in some verb forms occurs when the morpheme न(na) is prefixed to the verbs. Some of such verb forms are given below.

Negation due to Suffixation

Negation in Nepali verbs can also occur due to suffixation of the morpheme न(na) to verb forms/ verb roots. The morpheme can occur either at the end or in the middle of the negated verb.

For the following verb forms, negation occurs due to suffixation.

References

A Computational Analysis of Nepali Morphology: A Model for Natural Language Processing

Nepali verbs inflect to encode: Tense, Aspect, Mood, Person, Number, Gender and Honorifics.

Tense (काल)

In Nepali, verbs exhibit three tenses to signify the timing of an action in relation to the moment of speaking: Past (भुत काल), Present (वर्तमान काल) and Future (भविष्यत काल).

Past (भुत काल): खायो (khaa-yo)
Present (वर्तमान काल): खान्छ (khaa-n-cha)
Future (भविष्यत काल): खानेछु (khaa-ne-chu)

Aspect (पक्ष)

While tense tells us when an action occurs, aspect tells us how that action unfolds or is perceived. In Nepali, verbs can be inflected to express 4 aspects: Perfect (पूर्ण पक्ष), Habitual (अभ्यस्त पक्ष), Imperfect (अपूर्ण पक्ष) and Inferential (अज्ञात पक्ष).

Perfect Aspect (पूर्ण पक्ष)

The perfect aspect of a verb indicates that the action has been completed prior to the current moment. In Nepali grammar, the presence of the suffix "एको" (eko) signals the perfect aspect. Notably, the suffix "एको" (eko) undergoes inflection to match the number (singular or plural) and gender (masculine or feminine) of the subject involved in the action. Examples: खाएको (khaa-eko), खाएका (khaa-yeka)

Examples of Perfect Aspect (पूर्ण पक्ष) Verbs
खाएको (kha-eko) - masculine, singular
खाएका (kha-eka) - masculine, plural
खाएकी (kha-eki) - feminine, singular
खाएका (kha-eko) - feminine, plural

Imperfect Aspect (अपूर्ण पक्ष)

Imperfect aspect denotes an action that is in progress or ongoing. In Nepali grammar, this aspect is indicated by specific suffixes such as "दै" (dai), "दो" (do), "दी" (dii), and "दा" (da). These suffixes serve to highlight the ongoing nature of the action, suggesting that it is not yet complete or finalized. Examples: खाँदै (khaa-dai), खाँदा (khaa-daa)

Examples of Imperfect Aspect (पूर्ण पक्ष) Verbs
खाँदो(kha-do), खाँदै(kha-dai) - masculine, singular
खाँदा(kha-da), खाँदै(kha-dai) - masculine, plural
खाँदी(kha-di), खाँदै(kha-dai) - feminine, singular
खाँदा(kha-da), खाँदै(kha-dai) - feminine, plural

Habitual Aspect (अभ्यस्त पक्ष)

Habitual aspect depicts actions that occur regularly or habitually. It conveys the idea of actions that are customary or repeatedly performed. In Nepali grammar, the habitual aspect is represented by variants of the suffixes "छ" (cha) and "थ्" (th). These suffixes inflect to encode the person, number, gender, and levels of honorifics associated with the subject.

Examples of Habitual Aspect (अभ्यस्त पक्ष) Verbs
खान्छु (kha-n-chu), खान्थे (kha-n-the) - first person, inclusive, singular
खान्छौ (kha-n-chau) - first person, inclusive, plural
खान्थिस् (kha-n-this) - second person, masculine, singular
खान्थ्यौ (kha-n-theu) - second person, masculine, plural
खान्थ्यो (kha -n-thyo), खान्थे (kha-n-the) - third person, masculine, singular
खान्थे (kha-n-the) - third person, inclusive, plural
खान्थि (kha-n-thi), खान्थिन् (kha-n-thin) - third person, feminine, singular

Inferential Aspect (अज्ञात पक्ष)

Inferential aspect in Nepali is used to describe actions that have occurred in the past but are only known or inferred in the present, often based on indirect evidence or hearsay. In Nepali grammar, the occurrence of the suffixes "ए" (e) and "इ" (i) between the verb stem and the forms of "छ" (cha) indicates the inferential aspect. These suffixes serve to imply that the action, while not directly observed or experienced, is deduced or inferred to have taken place.

Examples of Inferential Aspect (अज्ञात पक्ष) Verbs
खाएछु (kha-e-chu) - first person, inclusive, singular
खाएछौँ (kha-e-chau)- first person, inclusive, plural
खाएछस् (kha-e-chas) - second person, masculine, singular
खाइछस् (kha-i-chas)  - second person, feminine, singular
खाएछौ (kha-e-chau) - second person, inclusive, plural
खाएछ (kha-e-cha) - third person, masculine, singular
खाइछ (kha-i-cha)  - third person, feminine, singular
खाएछन् (kha-e-chan) - third person, inclusive, plural

Mood (भाव)

Mood conveys the speaker's attitude or stance towards the content being communicated. In Nepali, verbs exhibit three moods, each indicating a different perspective or intention of the speaker: Imperative (आज्ञार्थ भाव), Optative (इच्छार्थ भाव), and Potential (सम्भावनार्थ भाव).

Imperative Mood (आज्ञार्थ भाव)

Imperative Mood express commands or requests. It is a directive form that directs the listener to perform a certain action. Verbs in the imperative mood undergo inflection to match the number and honorifics associated with the subject or the individual being addressed.

Examples of Imperative Mood (आज्ञार्थ भाव) Verbs
खा (kha) - singular, informal
खानुहोस् (khaanu hos) - singular, formal
खाओ(kha-o) - plural, inclusive
खानुहोस् (khaanu hos) - plural, formal, inclusive

Optative Mood (इच्छार्थ भाव)

Optative mood indicates wishes, hopes, or desires. It allows speakers to express their desires regarding a particular situation or outcome. Optativer forms also undergo inflection to align with the person, number, and level of honorifics involved in the communication.

Examples of Optative Mood (इच्छार्थ भाव) Verbs
खाउँ (kha-u) - first person, singular/plural
खाएस् (kha-esh) - second person, singular
खाए (kha-e) - second person, plural
खाओस् (kha-os) - third person, singular
खाउन् (kha-un) -  third person, plural

Potential Mood (सम्भावनार्थ भाव)

Potential mood in language serves as a means to convey the possibility or likelihood of an action occurring. This mood allows for the expression of hypothetical scenarios or speculative statements about what may happen. In Nepali grammar, verbs inflect to indicate the potential mood, adapting to align with the person, gender, and number of the subject involved in the action.

Examples of Potential Mood (सम्भावनार्थ भाव) Verbs
खाउँला (kha-u-la) - first person, inclusive, singular
खाऔँला (kha-aula) - first person, inclusive, plural
खालास् (kha-lash) - second person, masculine, singular
खालिस् (kha-lish) - second person, feminine, singular
खाऔला (kha-aula) - second person, inclusive, plural
खाला (kha-la) - third person, masculine, singular
खाली (kha-li) - third person, feminine, singular
खालान् (kha-lan) - third person, inclusive, plural

Person

In Nepali grammar, verbs undergo inflection in agreement with person. It distinguishes between the first person (the speaker), the second person (the recipient or addressee), and the third person (others not involved in the conversation). Person verbs also demonstrate variations based on mood, tense, aspect, and number. In addition, second and third person verbs also inflect for gender and grades of honorifics.

Examples of First Person Verbs
खाए (kha-e) - past tense, singular
खान्छु (kha-n-chu) - present tense, singular
खानेछु (kha-ne-chu) - future tense, singular
खायौँ (kha-you)  - past tense, plural
खान्छौँ (kha-n-chau) - present tense, plural
खाने छौँ (kha-ne-chau) - future tense, plural

Examples of Second Person Verbs
खाइस् (kha-i-sh) - past tense, inclusive, singular
खान्छस् (kha-n-chas) - present tense, masculine, singular
खान्छेस् (kha-n-ches) - present tense, feminine, singular
खानेछस् (kha-ne-chas) - future tense, masculine, singular
खानेछेस् (kha-ne-ches) - future tense, feminine, singular
खायौ (kha-you)  - past tense, inclusive, plural
खान्छौ(kha-n-chau) - present tense, inclusive, plural
खाने छौ (kha-ne-chau) - future tense, inclusive, plural

Examples of Third Person Verbs
खाइस् (kha-i-sh) - past tense, inclusive, singular
खान्छस् (kha-n-chas) - present tense, masculine, singular
खान्छेस् (kha-n-ches) - present tense, feminine, singular
खानेछस् (kha-ne-chas) - future tense, masculine, singular
खानेछेस् (kha-ne-ches) - future tense, feminine, singular
खायौ (kha-you)  - past tense, inclusive, plural
खान्छौ(kha-n-chau) - present tense, inclusive, plural
खाने छौ (kha-ne-chau) - future tense, inclusive, plural

Number

Nepali verbs exhibit agreement with the subject in terms of number: singular and plural.

Examples of Singular Verbs
खाइस् (kha-i-sh) - past tense, inclusive
खान्छस् (kha-n-chas) - present tense, masculine
खान्छेस् (kha-n-ches) - present tense, feminine, singular
Examples of Plural Verbs
खायौ (kha-you)  - past tense, inclusive, plural
खान्छौ(kha-n-chau) - present tense, inclusive, plural
खाने छौ (kha-ne-chau) - future tense, inclusive, plural

Gender

Verbs inflect to demonstrate two forms of gender agreement: masculine and feminine, reflecting the gender of the subject. This distinction is particularly evident in the conjugation of verbs for the second and third person singular forms.

Honorifics

In Nepali language, honorifics play a significant role in social interactions, influencing verb forms to express different levels of respect in speech. Second and third person verb forms can undergo inflection to reflect three distinct grades of honorifics: casual, familiar, and respectful. These honorifics are chosen based on the level of formality and the relationship between the speaker and the listener.

Casual Honorifics

Casual honorifics are used when addressing juniors or friends in a casual setting. The language used is informal and relaxed, reflecting a close relationship between the speaker and the listener.

तँ (You, singular) - Casual Honorific
  तँ खान्छस् (kha-n-chas)

Familiar Honorifics

The second grade of honorific, familiar honorifics, is employed when speaking to friends, acquaintances, or colleagues. It is more formal compared to casual honorifics and is considered appropriate for most social interactions.

तिमी (You, singular) - Familiar Honorific
  तिमी खान्छौ (kha-n-chau)

Respectful Honorifics

Respectful honorifics are used while addressing seniors or elders, as well as individuals deserving of utmost respect. Verbs inflected with respectful honorifics exhibit a high level of respect and formality.

हजुर (You, singular) - Respectful Honorific
  हजुर खानुहोस् (kha-nu-hos)

Recap: Inflectional Morphemes

• Inflectional morphemes encode grammatical meaning like gender, number, tense, person, and levels of honorifics.

• Inflectional forms of a word have the same meaning as the root.

• Inflectional morphemes have a transparent and regular function such that they do not change the lexical category.

• Since inflection encode grammatical meaning, they do not precede derivational morphemes.

• In Nepali, there are only inflectional suffixes.

Inflections in Nepali Nouns and Pronouns

Nepali nouns and pronouns inflect for seven cases (कारक): Nomiantive, Accusative, Instrumental, Dative, Ablative, Genitive and Locative and number (वचन): Singular, Plural. All of thses inflectional forms are marked by postpositions.

1. Nominative Case (कर्ता) Nominative case is used to indicate the subject of a sentence, or the doer of an action.

साथीले (sathi-le) - noun with nominative, singular
साथीहरुले (sathi-haru-le) - noun nominative case, plural
तिमीले (timi-le) - pronoun nominative case, singular
तिमीहरुले (timi-haru-le) - pronoun nominative case, plural

2. Accusative Case (कर्म) The accusative case marks the direct object of a verb, the receiver of the action.

साथीलाई (sathi-lai:) - noun with accusative, singular
तिमीलाई (timi-lai:) - pronoun with accusative, singular
साथीहरुलाई (sathi-haru-lai:) - noun with accusative, plural
तिमीहरुलाई (timi-haru-lai:) - pronoun with accusative, plural

3. Instrumental Case (करण) The instrumental case denotes the instrument or means by which an action is performed.

साथीले (sathi-le) - noun with instrumental, singular
साथीहरुले (sathi-haru-le) - noun instrumental case, plural
तिमीले (timi-le) - pronoun instrumental case, singular
तिमीहरुले (timi-haru-le) - pronoun instrumental case, plural

4. Dative Case (सम्प्रदान) Dative case indicates the indirect object of a verb, the recipient of the action.

साथीलाई (sathi-lai:) - noun with dative, singular
तिमीलाई (timi-lai:) - pronoun with dative, singular
साथीहरुलाई (sathi-haru-lai:) - noun with dative, plural
तिमीहरुलाई (timi-haru-lai:) - pronoun with dative, plural

5. Ablative Case (अपादान) The ablative case expresses the origin, source, or cause of an action.

साथीदेखि (sathi-dekhi), साथीबाट (sathi-bata) - noun with ablative, singular
तिमीदेखि (timi-dekhi), तिमीबाट (timi-bata) - pronoun with ablative, singular
साथीहरुदेखि (sathi-haru-dekhi), साथीहरुबाट (sathi-haru-bata) - noun with ablative, plural
तिमीहरुदेखि (timi-haru-dekhi),  तिमीहरुबाट (timi-haru-bata) - pronoun with ablative, plural

6. Genitive Case (सम्बन्ध) The genitive case signifies possession, association, or belonging.

साथीको (sathi-ko) - noun with genitive, singular
उनको (un-ko) - pronoun with genitive, singular
साथीहरुको (sathi-haru-ko) - noun with genitive, plural
उनीहरुको (uni-haru-ko) - pronoun with genitive, plural

7. Locative (अधिकरण) The locative case indicates location or place where something happens or is located.

साथीमा (sathi-ma) - noun with locative, singular
उनीमा (uni-ma) - pronoun with locative, singular
साथीहरुमा (sathi-haru-ma) - noun with locative, plural
उनीहरुमा (uni-haru-ma) - pronoun with locative, plural

Inflections in Nepali Adjectives

Nepali adjectives inflect for number (Singular, Plural) and gender (Masculine and Feminine) and seven cases of the nouyn they modify. It involves transforming singular adjectives ending in "o" to their plural counterparts ending in "a", and masculine adjectives with "o" ending to feminine adjectives with "i" ending. For instance, the adjective "राम्रो" (ramro), meaning "good" in singular masculine form, becomes "राम्रा" (ramra) in its plural form and "राम्री" (ramri) in its feminine form. See Table 2 for a detailed overview of inflectional patterns in Nepali adjectives.

राम्रो (ramr-o) - singular, masculine
राम्री (ramr-i) - singular, feminine
राम्रा (ramr-a) - plural, masculine
राम्रा (ramra) - plural, feminine

Note: A free morpheme is a standalone word and has a meaning of its own. However, a bound morpheme by itself cannot be considered a word even though it may carry some meaning.

Inflections v/s Derivations

• Inflectional morphemes encode grammatical meaning, hence inflectional forms of a word have the same meaning as the root.

• Inflectional morphemes have a transparent and regular function such that they do not change the lexical category.

• Since inflection encode grammatical meaning, they do not precede derivational morphemes.

• In Nepali, there are only inflectional suffixes.

स्कुल (school) + हरु (haru) = स्कुलहरु (school-haru) # Plural Form
स्कुल (school) + को (ko) = स्कुलको (school-ko) # Genetive Form

• Derivational morphemes carry lexical meaning, hence when such morphemes combine with free morphemes they form new words.

• Derivational morphemes may also change the lexical category of the root.

• In Nepali, there are derivational prefixes and suffixes.

# Prefix
अनु (anu) + रुप (rup) = अनुरुप (anu-rup)
अभि (abhi) + योग (yog) = अभियोग (abhi-yog)

# Suffix
बच् (bach) + अत (ata) = बचत (bach-ata) # Verb to Noun
ठग् (thag) + आहा (aahaa) = ठगाहा (thag-aahaa) # Verb to Adjective

NOTE: There are no derivational/inflectional infixes and circumfixes in Nepali.

Form and Structure Classes

In addition to inflection and derivation, it's crucial to understand the concept of form and structure classes in Nepali. Form classes refer to words that primarily convey content and carry meaning, such as nouns, verbs, adjectives, and adverbs. These words usually undergo inflectional and derivational processes.

Structure classes, on the other hand, include function words like articles, conjunctions, prepositions, and pronouns. They contribute to the grammatical structure and organization of sentences but do not typically undergo inflectional or derivational changes.

Nepali is written using vowels, consonants, modifiers(मात्रा) and symbols(चिन्ह).

Nepali Alphabets

Nepali Alphabets consists of 11 vowels and 33 consonants. All the vowels and consonants, in Nepali, are listed in Table 1.

क्ष, त्र and ज्ञ are usually mistaken for consonants but these letters are special combination of two different consonants and halanta "्".

क + ् + ष = क्ष	
त + ् + र = त्र
ज + ् + ञ = ज्ञ

NOTE: In Nepali, there is no provision for uppercase and lowercase letters.

Modifiers(मात्रा)

Modifiers, in Nepali, are representations for vowels. A modifier is used when the vowel is preceded by a consonant. Vowels and their respective modifiers are given in Table 2.

These modifiers can appear at the foot, top or middle of a consonant. They can also appear before and after a consonant.

ु and ू can appear at the foot or middle of a consonant and ृ appears at the foot of a consonant.

At foot:

क + ु = कु
क + ू = कू
क + ृ = कृ

At middle:

र + ु = रु
र + ू = रू

ि appears before a consonant.

क + ि = कि

ा, ी, ो and ौ appear after a consonant.

क + ा = का
क + ी = की
क + ो = को
क + ौ = कौ

NOTE: Regardless of where the modifiers appear to be in writing, in computerized texts, consonants preced the modifiers.

Symbols(चिन्ह)

In addition to alphabets and modifiers, there are other symbols used in Nepali. Such symbols are listed below.

Chandrabindu(चन्द्रविन्दु) : ँ  
Sirbindu(शिरविन्दु): ं 
Halanta(हलन्त): ् 
Visarga(विसर्ग): : 

Chandrabindu and Sirbindu

Both, Chandrabindu and Sirbindu are used to indicate nasalization. Chandrabindu is usually used with vowels, indicating that the previous vowel is nasalized.

जाउँला
आउँछु

Sirbindu is usually used to before य, र, ल, व, श, ष, स and ह.

संयुक्त
संरचना
संलग्न
संवाद
वंश
संसार
हंश

Halanta

Every consonant has an inherent vowel; halanta is used to supress or cancel the occurrence of such vowels. Occurrence of halanta between two consonants, say C1 and C2, there can be three different cases of conjoined consonants.

In the first case, C1 and C2 fully conjoin to form a consonant with a visible halanta occurring at the foot of C1.

छङ्छङ
सङ्लो

Second, the half or modified form of C1 and the full form of C2 conjoin to give a consonant.

रत्न
निहत्था
भुल्क

Third, the full form C1 and the half or modified form of C2 conjoin to give a consonant.

प्रणाम
बज्र
छाप्रो

Visarga

Visarga is a frequent occurrence in sanskrit texts. In Nepali, a handful of words borrowed from sanskrit contains visarga. Few of such words are listed below.

दु:ख
नि:स्वार्थ
मूलत:
प्रथमत:

This sums up the basic introduction to written Nepali.

Sentence-level Tokenization

In cases where we want our tokens to be sentences, our possible token boundary is either पूर्णविराम(।) or प्रश्न चिन्ह(?) or विस्मयादिबोधक(!). So, by splitting the given text at पूर्णविराम(।) or प्रश्न चिन्ह(?) or विस्मयादिबोधक(!), sentence-level tokenization can be achieved.

पूर्णविराम(।) in Nepali is equivalent to a full stop (.) in English.

# Split at ?, । or !
return re.split('(?<=[।?!]) +', text)

INPUT: 
परिश्रम नगरी हुन्छ? परिश्रम सफलताको एक मात्र बाटो हो। जो परिश्रम गर्छ, उही सफल हुन्छ। अब त परिश्रम गर्छौ नि? नगरी कहाँ हुन्छ त!

OUTPUT:
['परिश्रम नगरी हुन्छ?', 'परिश्रम सफलताको एक मात्र बाटो हो।', 'जो परिश्रम गर्छ, उही सफल हुन्छ।', 'अब त परिश्रम गर्छौ नि?', 'नगरी कहाँ हुन्छ त!']

You can find out more about punctuation marks in Nepali at: [Punctuation in Nepali] (https://nepalgo.tumblr.com/post/71951951192/punctuation-marks).

Word-level Tokenization

In languages that have words separated by blank spaces, the token boundary for word-level tokenization is the blank/white space. Nepali is one such language, so word-level tokenization in Nepali can be achieved by stripping tokens at those white spaces. However, it is not as simple as it looks, especially when dealing with punctuations. Some punctuation is easy to handle. All that you need to do is replace them with a white space and you are good to go.

Cases involving hyphen (-) and colon (:) need to be handled differently.

Replacing Punctuations with White Space

The following is the list of punctuations that can be handled by simply replacing them with a white space.

,
)
(
{
}
[]
!
‘
’
“
”
:-
?
।
/
—

INPUT:
राम आयो र भन्यो, "दाइ र दिदि, यति दिन कता हुनुहुन्थ्यो?" तब, दाइ/दिदिले केहि नबोली आफ्नो (बाटो) लाग्नुभयो।

OUTPUT:
['राम', 'आयो', 'र', 'भन्यो', 'दाइ', 'र', 'दिदि', 'यति', 'दिन', 'कता', 'हुनुहुन्थ्यो', 'तब', 'दाइ', 'दिदिले', 'केहि', 'नबोली', 'आफ्नो', 'बाटो', 'लाग्नुभयो']

Hyphen (-)

In Nepali, a Hyphen (योजक चिन्ह) is used in linking word pairs: opposite, analogy or similar, together. In such cases, the hyphen is considered as a part of the token itself.

जीवन-प्रक्रिया

आ-आफ्नो

स-सानो

However, in many online texts, hyphens are also being used in place of one of the निर्देशक चिन्ह: dash (—). In this case, there are two ways in which a hyphen is used.

For the first case, the hyphen occurs independently.

# Independent hyphen i.e. not attached to the word
आक्रोश - घाम

In case, as shown above, the hyphen is simply replaced with a white space.

In the second case the hyphen is attached to the end of a word. In such cases the hyphen is tokenized with the word as a part of the word and then all the hyphens that occurs as the last character in the token is removed.

if word[len(word) - 1:] == '-':
    words.append(word[:len(word) - 1])

INPUT: 

आ-आफ्नो बाटो लागे- भन्दै - श्यामपनि आफ्नो बाटो हिड्यो।

OUTPUT:

['आ-आफ्नो', 'बाटो', 'लागे', 'भन्दै', 'श्यामपनि', 'आफ्नो', 'बाटो', 'हिड्यो']

Colon(:)

Colon in Nepali, can occur as a part of word or as निर्देशक चिन्ह in place of a dash(—). Colon, which is a part of word can appear either in between or at the end of the word. Some of such words are listed below.

दु:ख
नि:स्वार्थ
मूलत:
प्रथमत:
क्रमश:

For colon that appear as in place of dash, they have two cases similar to the ones discussed above in hyphen. The first case is handled in the same way the first case of hyphen was handled i.e. by replacing the punctuation with a white space. However, handling the second case where colon appears as the last character of the word is a little tricky because it is difficult to identify if is a part of the word or is used in place of a dash. Since, a handful of words in Nepali end with colon, the current tokenizer uses a lexicon of such words to to understand if the end-of-word colon is a part of the word or is it used in place of a dash.

The colon is replaced with a white space if the word doesn't exist in the lexicon of words.

if word[len(word) - 1:] == ':' and word not in colon_lexicon:
    words.append(word[:len(word) - 1])
else:
    words.append(word)

INPUT:

यस्ता छन्: प्रथमत: नि:स्वार्थ।

OUTPUT: 

['यस्ता', 'छन्', 'प्रथमत:', 'नि:स्वार्थ']

Period(.)

Period is another punctuation used in Nepali. Unlike in English where a period can be used in two cases: ending a sentence i.e. as a fullstop and as a part of abbreviation, in Nepali it is used for latter only.

गा.वि.स.
डा.
कि.मी.

So, for tokenization of Nepali texts, period is considered as a part of the token itself.