Nondeclinable

Nondeclinable, also referred to as indeclinable, is a term in linguistics used to describe words that do not undergo grammatical inflection in a given language. This means such words do not change form to signal case, number, gender, tense, mood, or other grammatical categories. Nondeclinable items contrast with declinable words, which alter their form to express grammatical relationships within a sentence.

Common categories that are typically nondeclinable include adverbs, prepositions, conjunctions, interjections, and many particles. In addition, abbreviations, some foreign loanwords, and certain numerals can be treated as indeclinable in particular languages. Some languages also have small subgroups of adjectives or numerals that appear invariable in specific contexts, though this is less common.

In linguistic analysis, nondeclinable words often function as function words or particles rather than content words. They establish syntactic or semantic relationships without encoding grammatical information through morphology themselves. Their invariance can simplify production and recognition of sentence structure in some cases, but it can also pose challenges for parsing and knowledge representation, especially in languages with rich inflection where the surrounding words carry most of the grammatical information.

Usage and documentation: grammars and dictionaries commonly label words as nondeclinable to indicate their lack of inflection. This classification helps describe a language’s morphology and guides analysis of syntax and word formation.

See also: declension, inflection, indeclinable (alternative term).