Noun phrases usually need a framing element. A determiner is a word that introduces a noun and specifies aspects of reference such as definiteness, quantity, possession, or proximity.

Articles, demonstratives, possessives, and quantifiers commonly function as determiners. In English a determiner typically occupies the slot before adjectives and the noun: those three blue books. Some languages allow determiner stacking; others restrict the position tightly or lack a dedicated class.

Determiners interact with noun semantics and information structure. Learners must sort out subtle contrasts among quantifiers and articles. Syntactic theories often treat the determiner as the head of its own phrase, reflecting its structural importance in the noun phrase.

• Word that specifies reference of a noun phrase
• Includes articles, demonstratives, and quantifiers
• Usually precedes adjectives and the noun in English
• Central to noun-phrase structure