wordclass

Word class, or part of speech, is a grammatical category that groups words by their syntactic function and behavior in sentences. Word classes help describe how words combine with others to form phrases and how they carry grammatical information such as number, tense, or agreement.

Common word classes include nouns, pronouns, verbs, adjectives, adverbs, determiners, numerals, prepositions, conjunctions, and interjections. In many languages, nouns and pronouns denote things or people; verbs encode actions or states; adjectives modify nouns; adverbs modify verbs, adjectives, or other adverbs; determiners mark reference; prepositions express relationships; conjunctions join elements; interjections express emotion.

Word classes are often divided into open and closed classes. Open classes (nouns, verbs, adjectives, adverbs) readily borrow new members; closed classes (pronouns, determiners, prepositions, conjunctions, numerals, interjections) resist new members.

Words can be polyfunctional, shifting class by use. For example, run can be a noun or a verb; fast can function as an adjective and adverb. Some languages also show category shifts with function words or particles.

Cross-linguistically, word class systems vary. Some languages rely heavily on morphology to mark function, others depend more on word order or case. Descriptions of word classes may differ across linguistic traditions, but the core idea remains: classify words by distribution and syntactic role.

In computational linguistics, word classes underpin part-of-speech tagging and parsing, enabling software to infer syntax, semantics, and relationships in text.