In linguistics, derivation is the process of forming a new word on the basis of an existing word, e.g. happi-ness and un-happy from happy, or determination from determine. Derivation stands in contrast to the process of inflection, which uses another kind of affix in order to form grammatical variants of the same word, as with determine/determine-s/determin-ing/determin-ed. Generally speaking, inflection applies to all members of a part of speech (e.g., every English verb has a past-tense form), while derivation applies only to some members of a part of speech (e.g., the nominalizing suffix -ity can be used with the adjectives modern and dense, but not with open or strong).
A derivational suffix usually applies to words of one syntactic category and changes them into words of another syntactic category. For example, the English derivational suffix -ly changes adjectives into adverbs (slow → slowly).
Examples of English derivational patterns and their suffixes:
- adjective-to-noun: -ness (slow → slowness)
- adjective-to-verb: -ise (modern → modernise) in British English or -ize (archaic → archaicize) in American English and Oxford spelling
- adjective-to-adjective: -ish (red → reddish)
- adjective-to-adverb: -ly (personal → personally)
- noun-to-adjective: -al (recreation → recreational)
- noun-to-verb: -fy (glory → glorify)
- verb-to-adjective: -able (drink → drinkable)
- verb-to-noun (abstract): -ance (deliver → deliverance)
- verb-to-noun (concrete): -er (write → writer)
Although derivational affixes do not necessarily alter the syntactic category, they do change the meaning of the base. In many cases, derivational affixes change both the syntactic category and the meaning: modern → modernize ("to make modern"). The change of meaning is sometimes predictable: Adjective + ness → the state of being (Adjective); (white→ whiteness).
A prefix (write → re-write; lord → over-lord) will rarely change syntactic category in English. The inflectional prefix un- applies to adjectives (healthy → unhealthy)and some verbs (do → undo), but rarely to nouns. A few exceptions are the derivational prefixes en- and be-. En- (em- before labials) is usually used as a transitive marker on verbs, but can also be applied to adjectives and nouns to form transitive verbs: circle (verb) → encircle (verb); but rich (adj) → enrich (verb), large (adj) → enlarge (verb), rapture (noun) → enrapture (verb), slave (noun) → enslave (verb).
Note that derivational affixes are bound morphemes. In that respect, derivation differs from compounding by which free morphemes are combined (lawsuit, Latin professor). It also differs from inflection in that inflection does not create new lexemes but new word forms (table → tables; open → opened).
Derivation can occur without any change of form, for example telephone (noun) and to telephone. This is known as conversion or zero derivation.