A determiner is a word that modifies a noun or a noun phrase. The determiners express relationship or reference of noun or noun phrase in the context.
Determiners include the following:
1. Articles (a, an, and the)
There are two types of articles - definite and indefinite. ‘The’ is definite article, whereas ‘a’ and ‘an’ are indefinite articles.
2. Demonstrative Pronouns (this, that, these, and those)
3. Possessive Pronouns (like your, my, their, and her)
4. Quantifiers (like many, some, few, and several)
Quantifiers are commonly used before either countable or uncountable nouns.
Like determiners, adjectives also modify nouns. So what’s the difference? Adjectives express attributes, whereas determiners express relationships. You can also classify determiners as certain types of adjectives. Some grammarians do not consider determiners as adjectives, but give them a class of their own. Usually, you cannot use more than one determiner in the same noun phrase.