Study the situation below:

Pam: My friend bought a schoolbag and an umbrella yesterday.

          The schoolbag was very useful but the umbrella was too big.

We use a before words that begin with a consonant and an before words that begin with a vowel.

Pam uses a and an because it is the first time when she talks about those items.

In the second sentence she uses the because she knows which schoolbag and which umbrella she means – the ones her friend bought yesterday.

We use the when we are talking about a specific thing, person, place, etc.

example: He went to the doctor.( = to his usual doctor)

Do you know a good doctor in the neighborhood?

He is a manager.

Could I speak to the manager, please? ( = the manager of that company)

We also use the when is the only one of something, such as the Sun, the equator, the Moon, the capital of Romania, the end of this year, the end of the road, etc.

Exceptions:

• We use the before same: My bag is the same as yours.
• We usually say the theatre (I went to the theatre last night.), the cinema (I went to the cinema.) but we don’t necessarily mean a specific theatre or cinema.