In linguistic morphology, inflection (less commonly, inflexion) is a process of word formation in which a word is modified to express different grammatical categories such as tense, case, voice, aspect, person, number, gender, mood, animacy, and definiteness. The inflection of verbs is called conjugation, whereas the inflection of nouns, adjectives, adverbs, etc. can be called declension.
An inflection expresses grammatical categories with affixation (such as prefix, suffix, infix, circumfix, and transfix), apophony (as with Indo-European ablaut), or other modifications. For example, the Latin verb , meaning 'I will lead', includes the suffix , expressing person (first), number (singular), and tense-mood (future indicative or present subjunctive). The use of this suffix is an inflection. In contrast, in the English clause "I will lead", the word lead is not inflected for any of person, number, or tense; it is simply the bare form of a verb. The inflected form of a word often contains both one or more free morphemes (a unit of meaning which can stand by itself as a word), and one or more bound morphemes (a unit of meaning which cannot stand alone as a word). For example, the English word cars is a noun that is inflected for number, specifically to express the plural; the content morpheme car is unbound because it could stand alone as a word, while the suffix -s is bound because it cannot stand alone as a word. These two morphemes together form the inflected word cars.
Words that are never subject to inflection are said to be invariant; for example, the English verb must is an invariant item: it never takes a suffix or changes form to signify a different grammatical category. Its categories can be determined only from its context.
Requiring the forms or inflections of more than one word in a sentence to be compatible with each other according to the rules of the language is known as agreement or concord. For example, in "the man jumps", "man" is a singular noun, so "jump" is constrained in the present tense to use the third person singular suffix "-s".
Languages that have some degree of inflection are called synthetic languages. They can be highly inflected (such as Georgian or Kichwa), moderately inflected (such as Russian or Latin), weakly inflected (such as English), but not uninflected (such as most varieties of Chinese). Languages that are so inflected that a sentence can consist of a single highly inflected word (such as many Native American languages) are called polysynthetic languages. Languages in which each inflection conveys only a single grammatical category, such as Finnish, are known as agglutinative languages, while languages in which a single inflection can convey multiple grammatical roles (such as both nominative case and plural, as in Latin and German) are called fusional languages.
Weakly inflected languages which seldom make use of inflection, such as English, are said to be analytic. Analytic languages that do not make use of derivational morphemes, such as Standard Chinese, are said to be isolating. Highly synthetic languages are weakly or not at all analytic and vice-versa, while a middle-ground language like English may exhibit traits of both to varying degrees.
Examples in English Most native-English nouns are inflected for number with the inflectional plural affix -[e]s (as in dogs ← dog + -s; "glasses" ← glass + -es); most other English nouns are inflected for plurality in some other way, varying by language of loanword origin. Most English verbs are inflected for tense with the inflectional past tense suffix -ed (as in called ← call + -ed). English also inflects verbs by suffixation to mark the third-person singular in the present tense (with -s), and the present participle (with -ing, also used for gerunds). Some English adjectives (mostly those derived from Anglo-Saxon) are inflected to mark comparative and superlative forms, with -er and -est respectively (while those derived from other linguistic substrates, like French and Latin, are instead preceded by the separate words more and most, respectively – a non-inflected genitive construction).
There are eight regular inflectional affixes in the English language.
+Inflectional affixes in EnglishAffixGrammatical categoryMarkPart of speech -s or -es (among other approaches from a loanword's origin language)Numberpluralnouns --'s or -' or (on pronouns only) -sCasegenitive (possessive)nouns and noun phrases; pronouns (marks independent possessive) -ingAspectprogressivegerunds or participles -ed or -enAspectperfectverbs -ed, uncommonly -t, or archaically/poetically -'dTensepast (simple)verbs -s or -esPerson, number, aspect, tense3rd person singular present indicativeverbs -er (replaced by more before most loanwords)Degree of comparisoncomparativeadjectives and adverbs -est (replaced by most before most loanwords)Degree of comparisonsuperlativeadjectives and adverbs
Despite the march toward regularization, modern English retains traces of its ancestry, with a minority of its words still using inflection by ablaut (sound change, mostly in verbs) and umlaut (a particular type of sound change, mostly in nouns), as well as long–short vowel alternation. For example:
write, wrote, written (marking by ablaut variation, and also suffixing in the participle) sing, sang, sung (ablaut) foot, feet (marking by umlaut variation) mouse, mice (umlaut) child , children (ablaut, and also suffixing in the plural)
Regular and irregular inflection When a given word class is subject to inflection in a particular language, there are generally one or more standard patterns of inflection (the paradigms described below) that words in that class may follow. Words which follow such a standard pattern are said to be regular; those that inflect differently are called irregular.
For instance, many languages that feature verb inflection have both regular verbs and irregular verbs. In English, regular verbs form their past tense and past participle with the ending -[e]d. Therefore, verbs like play, arrive, and enter are regular, while verbs like sing, keep, and go are irregular. Irregular verbs often preserve patterns that were regular in past forms of the language, but which have now become anomalous; in rare cases, there are regular verbs that were irregular in past forms of the language.
Other types of irregular inflected form include irregular plural nouns, such as the English plurals mice, children, and women and the French (the plural of , 'eye'); and irregular comparative and superlative forms of adjectives or adverbs, such as the English better and best (which correspond to the positive forms good or well).
Irregularities can have four basic causes:
Euphony: Regular inflection would result in forms that sound esthetically unpleasing or are difficult to pronounce (English far → farther or further; Spanish → , vs. → , ; Portuguese vs. Spanish (in both languages) → Portuguese vs. Spanish ). Principal parts: These are generally considered to have been formed independently of one another, so they must be memorized when learning a new word and its inflections. Example: Latin → Spanish . Strong vs. weak inflection: In some cases, two inflection systems exist, conventionally classified as "strong" and "weak". For instance, English and German have weak verbs that form the past tense and past participle by adding an ending (English jump → jumped; German → ); versus strong verbs that change vowel, and in some cases form the past participle by adding (English swim → swam, swum; German → , ). Ancient Greek verbs are likewise said to have had a first aorist () and a second aorist (). Suppletion: The "irregular" form was originally derived from a different root (English person → people). The comparative and superlative forms of good in many languages display this phenomenon (e.g. English good, better, best).
Declension and conjugation
Two traditional grammatical terms refer to inflections of specific word classes:
Inflecting a noun, pronoun, adjective, adverb, article, or determiner is known as declining it. The forms may express number, case, gender, or degree of comparison. Inflecting a verb is called conjugating it. The forms may express tense, mood, voice, aspect, person, or number.
An organized list of the inflected forms of a given lexeme or root word is called its declension if it is a noun, or its conjugation if it is a verb.
Below is the declension of the English pronoun I, which is inflected for case and number.
singular plural nominative I we oblique me us possessive determiner my our possessive pronoun mine ours reflexive myself ourselves
The pronoun who is also inflected according to case. Its declension is defective, in the sense that it lacks a reflexive form.
singular and plural nominative who oblique whom (traditional), who (informal) possessive whose reflexive –
The following table shows the conjugation of the verb to arrive in the indicative mood; suffixes inflect it for person, number, and tense:
TenseIyouhe, she, itweyouthey Present arrivearrivearrivesarrivearrivearrive Past arrivedarrivedarrivedarrivedarrivedarrived
The non-finite forms arrive (bare infinitive), arrived (past participle), and arriving (present participle, gerund), although not inflected for person or number, can also be regarded as part of the conjugation of the verb to arrive. Compound verb forms, such as I have arrived, I had arrived, or I will arrive, can be included also in the conjugation of the verb for didactic purposes, but they are not overt inflections of arrive. The formula for deriving the covert form, in which the relevant inflections do not occur in the main verb, is:
Conjugations of verbs in other languages are often much more complex, as illustrated below.
Inflectional paradigm An inflectional paradigm refers to a pattern (usually a set of inflectional endings), in which a class of words follows the same pattern. Nominal inflectional paradigms are called declensions, and verbal inflectional paradigms are termed conjugations. For instance, there are five types of Latin declension. Words that belong to the first declension usually end in -a and are usually feminine, these words share a common inflectional framework. Meanwhile words that belong to the second declension end in -us, -um, or -er, and are usually masculine or neuter. In Old English, nouns are divided into two major categories of declension, the strong and weak ones, as shown below:
gender and number Masculine Neuter Feminine Singular Plural Singular Plural Singular PluralcaseStrong noun declension 'angel' 'ship' 'sorrow' Nominative Accusative / Genitive Dative caseWeak noun declension 'name' 'eye' 'tongue' Nominative Accusative Genitive Dative
The terms strong declension and weak declension are primarily relevant to well-known dependent-marking languages (such as the Indo-European languages, or Japanese). In dependent-marking languages, nouns in adpositional (prepositional or postpositional) phrases can carry inflectional morphemes.
In head-marking languages, the adpositions can carry the inflection in adpositional phrases. This means that these languages will have inflected adpositions. In Western Apache (San Carlos dialect), the postposition 'on' is inflected for person and number with prefixes:
Singular Dual Plural 1st 'on me' 'on us two' 'on us' 2nd 'on you' 'on you two' 'on you all' 3rd 'on him' – 'on them'
Compared to derivation
Inflection is the process of adding inflectional morphemes that modify a verb's tense, mood, aspect, voice, person, or number or a noun's case, gender, or number, rarely affecting the word's meaning or class. Examples of applying inflectional morphemes to words are adding -s to the root dog to form dogs and adding -ed to wait to form waited.