The, A/an

Indefinite and Definite Articles

The words a, an, and the are special adjectives called articles.

Indefinite Articles—a, an

an—used before singular count nouns beginning with a vowel (a, e, i, o, u) or vowel sound:

• an apple, an elephant, an issue, an orange

a—used before singular count nouns beginning with consonants (other than a, e, i, o, u):

• a stamp, a desk, a TV, a cup, a book

Definite Article—the

Can be used before singular and plural, count and non-count nouns 

1. Indefinite Article (a, an)

Used before singular nouns that are unspecified:

• a pencil
• an orange

Used before number collectives and some numbers:

• a dozen
• a gallon

Used before a singular noun followed by a restrictive modifier:

• a girl who was wearing a yellow hat

Used with nouns to form adverbial phrases of quantity, amount, or degree:

• I felt a bit depressed.

2. Definite Article (the)

Used to indicate a noun that is definite or has been previously specified in the context:

• Please close the door.
• I like the clothes you gave me.

Used to indicate a noun that is unique:

• Praise the Lord!
• The Columbia River is near here.

Used to designate a natural phenomenon:

• The nights get shorter in the summer.
• The wind is blowing so hard.

Used to refer to a time period:

• I was very naïve in the past.
• This song was very popular in the 1980s.

Used to indicate all the members of a family:

• I invited the Bakers for dinner.
• This medicine was invented by the Smiths.

The words a, an and the are types of adjectives called articles.

A and an are called indefinite articles.
A is used before singular count nouns.
A car, a book, a child, a holiday

An is used with count nouns beginning with a vowel sound.
An apple, an elephant and notice; an hour but a European. ( the 'h' in hour is silent. The 'e' in European is not a vowel sound)

Definite article – The

'The' is used before singular and plural, count and non-count nouns.

Indefinite article

A or an are used before singular nouns that are not specified (not mentioned before):
A pen, an orange
I saw a beautiful scarf that I had to buy.
I'd love a cup of tea.

A and an are used in adverbial phrases of amount, quantity, or degree:
The film was a bit disappointing.
I was a bit depressed.

A and an are used with collectives and some numbers:
A dozen, a litre

Definite article

The is used to indicate a noun that is definite or has been specified (mentioned) before in context:
The door is open.
I loved the presents I got for my birthday.

The is used to speak about things that are unique:
I live by the sea.
The sun is getting stronger in summer.

The is used to refer to a time period:
He was a very successful business man in the past.
I remember the 90s very well.