Determiner

DETERMINER

A determiner is a word, phrase or affix that occurs together with a noun or noun phrase and serves to express the reference of that noun or noun phrase in the context. That is, a determiner may indicate whether the noun is referring to a definite or indefinite element of a class, to a closer or more distant element, to an element belonging to a specified person or thing, to a particular number or quantity, etc. Common kinds of determiners include definite and indefinite articles (like the English the and a or an), demonstratives (this and that), possessive determiners (my and their), and quantifiers (many, few and several). See examples in the box on the right

Examples
The girl is a student. I've lost my keys. Some folks get all the luck. Which book is that? I only had twenty-seven drinks. I'll take this one. Both windows were open. http://en.wikipedia.org/wiki/Determiner