What is a determiner?

A determiner is a word that tells us which thing.

What are the determiners?

There are different types of determiners:
Articles (general vs. specific one): a, an, the
Demonstratives (which one): this, that, these, those
Possessive determiners (whose one): my, your, his, her, its, our, your
Quantifiers (how many): all, many, some, few, no

However, the basic idea remains: one word to tell people which thing.

a / ana box
thethe box
thisthis box
thatthat box
thesethese boxes
thosethose boxes
my / your / his / her / its / our / theirmy box
all / many / some / few / noall boxes

Examples of determiners

He ate a pizza.
(we don’t know which pizza)
He ate the pizza.
(we know which pizza)
This box is mine.
(the box here)
That box is mine.
(the box there)
These toys are broken.
(the toys here)
Those toys are broken.
(the toys there)
You kissed your girlfriend.
(the girlfriend who is yours)
You kissed my girlfriend.
(the girlfriend who is mine)
All dogs are stupid.
(every dog)
Some cats are stupid.
(not all, but some)
She took all the money.
(all of the money)
She took all his money.
(all the money which was his)