A, an, some, any, the, no article

Mean one.

singular countable nouns

Used before a noun to suggest a contrast with 2 or more.

Use "a" before a word that begins with a consonant sound.

a professor

a house

a student

a university

Use "an" before a word that begins with a vowel sound.

an author

an honor

an instructor

an undergraduate

Used for plural countable nouns and uncountable nouns

"Some" for polite requests and offers

I'll get some bowls of rice.

There aren't any trees.

Could I have some chips?

I'll get some rice.

Is there any space?

countable and uncountable nouns when it is important or clear which thing(s), person (people) we are talking about.

We saw some green birds and some brown birds.

The green birds were beautiful.

when there is information afterwards to identify the noun.

Ankara is the capital city of Turkey.

when the noun is the only one in the world or in the place where we are.

I saw the English teacher.

I saw it on the internet.

musical instruments

the piano

the violin

names of rivers, seas, mountain, ranges, deserts and groups of islands or states.

It's a picture of the Amazon

I'm going to the Sahara

The United Arab Emirates.

with plural countable nouns and uncountable nouns when talking in general.

He likes books and films.

Bread is made of flour, water, yeast and salt.

Before colors, sports, activities and meals.

Let's have breakfast.

I don't like yellow walls.

before countries, mountains, lakes, islands and continents.

This is Canada/Lake Geneva/Mount Fuji

EXCEPTIONS. The USA, The UK

before places when the function of the place is more important than the building.

The school is on fire.

Ted's at school.

My brother is in hospital for an operation.

The bus stops at the hospital.