kooskäänduvad

Kooskäänduvad is a term used in Estonian linguistics to describe a phenomenon of joint inflection in coordinated phrases. It denotes a situation in which two or more words that form a syntactic unit—often a noun and its modifiers such as adjectives, numerals, or pronouns—inflect together, producing a uniform ending across the whole phrase rather than independent endings for every element. The concept is mainly discussed in descriptive grammars of Estonian when analyzing how coordination affects the assignment of case, number and other inflectional categories.

The phenomenon is most commonly associated with noun phrases connected by conjunctions such as ja (and) or ning, and with numerals that influence the case form of the entire phrase. In practice, kooskäänduvus is often treated as a descriptive observation about actual usage rather than a prescriptive rule: speakers may exhibit joint inflection in informal speech or in older texts, while more formal or standard usage tends to rely on each word inflecting according to its own syntactic role. The occurrence and acceptance of joint inflection can thus vary with dialect, register, and context.

Etymology and scope: the term kooskäänduvus is formed from koos ('together') and käänduma ('to inflect'), reflecting the idea of inflection spreading across a coordinated unit. It is discussed within the wider study of coordination, agreement, and inflection in Estonian grammar.

See also: Estonian grammar, käänamine, koordinaatsioon.