Determiners are words like a, my, this, that, some, all, both, either, every, enough and several. They come at the beginning of noun phrases, but they are not adjectives.
There are two main groups of determiners.
Group A determiners
Group A determiners (also called pre-determiners) help to identify things.
articles: a/an, the
possessives: my, your, our, his, her, its, their, one’s, whose
demonstratives: this, that, these, those
We cannot put two Group A determiners together.
Group B determiners
Most of these are ‘quantifiers’: they say how much or how many we are talking about.
some, any, no
each, every, either, neither
much, many, more, most; a little, less, least; a few, fewer, fewest; enough; several
all, both, half
what, whatever, which, whichever
one, two, three etc.
We can put two Group B determiners together if the combination makes sense.