Determiners are words we put in front of a noun or noun phrase‏‎. They tell us about the number and type of items we are talking about and often restrict the use of the noun. They are also one of the main PoS categories, that is, one of the main categories in which English words‎ are grouped grammatically.

For example:

Without a determiner we would be talking about all cats. With a determiner we talk about only some cats. Maybe cats belonging to some people

my cat

your cats

And sometimes where those cats are:

this cat

those cats

Determiners usually come before the noun or at the beginning of the noun phrase and we can generally only use one determiner for a noun phrase.

Types of Determiners

We can group determiners into different categories.

Specific or General

Determiners can be further divided into specif and general.

Specific determiners include:

the definite article: the
the possessives: my, your, his, her, its; our, their
the demonstratives: this, that, these, those
the interrogative: which, whose

We use specific determiners when it is clear to both the speaker and the listener what exactly they are referring to.

Tom, did you lock the door?

Ooops sorry, I forgot.

Both the person asking and the person answering know which door they are talking about.

Those lovely flowers over there are from John.

Here again we know the specific flowers the speaker is referring to.

Her car is always at the mechanic’s.

Not any car but her car!

Which road did you take to come here?

The speaker is asking about a specific route.

General determiners include:

The indefinite article: a/an

The indefinite pronoun: any, another, other

the interrogative: what

When we are talking about things in general and neither the speaker nor the listener know much about the exact thing they are referring to, we use the general determiners.

Jane got herself a dog.

We don’t know much more about the dog. All we know is that she got one.

I’d like another cup of tea, please.

We use another to talk about an additional person or thing.

It’s not rocket science. Try it, other people have done it!

Other is the plural form of another and likewise it is used to talk about additional people or things.

Vegans don’t eat meat, fish or any food that comes from animals.

Any + food (a non-count noun) shows vegans don’t eat all of those food.

What have you been up to lately?

I have not seen you in a while and so I’m asking in general.