Determiners are small words used before nouns to tell us which one, or how many, or whose, and so on.
1. The man
2. A school girl
3. All people
4. Every chance
5. No peace
6. Some buttons
7. Any information
8. Both tigers
9. Your friends
10. Their money.
What are now known as determiners were formerly sometimes (confusingly) included among adjectives since they turn up in front of nouns. But that is almost all they have in common with adjectives.
Many determiners look like pronouns.
e.g. The word 'that' in the sentence "That idea is foolish" is a pronoun because it is on its own is a subject of the sentence.
The two common determiners are "the", "a/an" are called articles.
'The' is the definite article. It refers to a defined thing or person.
e.g. Get me the gun. (the one definite or specific or only gun)
'A' or 'an' is the indefinite article. The object or person it refers to is not defined.
e.g. Get me a gun ( any brand of gun will do).