Articles: The words A, An, and The are called articles. They come before nouns to make them Definite or Indefinite.

Ex: "A watch" means any watch, and 'the book" means a particular book.

Indefinite Articles (A or An):

• A or An is called the Indefinite article because it makes the noun Indefinite.

Ex: A watch, means any watch, since no information is available about the watch.

• The Indefinite article is used before singular countable nouns.

Ex: An apple, A book, A boy.

Ex: She is a dancer.

A vs An🧐

• The use of A and An is determined by the sound of nouns.
• A is used before a word beginning with a consonant sound.

Ex. a pen,  a paper, a book, etc.

• An is used before a word beginning with a vowel sound.

Ex: An apple, an umbrella, an X-ray, an M.A., etc.

Uses of "A/An":

• with idiomatic expressions like:

 A lot of, A great number of, A large number of, A number of, a good deal of, Have a sleep, have a walk, In a mood, in a hurry, make a noise, take a risk, etc.

Definite Article (The):

The definite article is used before a singular countable noun, plural countable noun, and uncountable noun to make it definite, which means to point out some particular person or thing.

Ex: the man (singular countable), the boys (plural countable), the milk (uncountable), etc.

Essential Uses of "The":

• Before river names ( Ex: The Ganga, The Cauvery)

• Before sea names ( Ex: The Red Sea, The Arabian Sea)

• Before ocean names ( Ex: The Indian Ocean, The Pacific Ocean)

• Before directions ( Ex: the east, the west)

• Before the island ( EX: the Andmans)

• Before famous or religious books ( Ex: The Ramayana)

• Before musical instruments ( Ex: The guitar, The violin)

• Before the name of specific government bodies( Ex: The supreme court)

• Before  superlative degree adjectives

Ex: the best, the tallest.

• With ordinal numbers which come before nouns ( Ex: The First, The Second)
• when comparing a proper noun

Ex: he is the dhoni of our team

•  The +comparative degree+subject+verb, the+comparative Degree+subject+verb

Ex: The faster she runs, the happier she feels.

Omission of articles:

• The articles are omitted before the subject, language, games, and sports names.

Ex: she is a student of English.

• Articles are not used When noun comes after kind of, type of, a large number of, lots of, a lot of, or a great deal of.

Ex: He felt kind of excitement before the big game.

• Generally, no article is used before proper nouns (specific names of people, places, or things).

• However, "the" may be used before a proper noun when the noun is used as a common noun.

Examples: "I visited India." (Proper noun), I visited the taj mahal. (Proper noun used as a common noun).

• Before the name of relations like father, mother, aunt, etc.

Ex: Father has returned.

•  The articles are omitted before school, college, university, church, and hospital when these places are used for their primary purpose.

Ex: I go to church on Mondays

Ex: I go to school daily.

• Articles are often omitted in certain fixed expressions, such as "at home," "by train," "in bed," and "at school."
• No articles are used after distributive adjectives (Each, either, neither, every)

Ex: Each boy is responsible for cleaning up his own mess. (correct).

Ex: Each a boy is responsible for cleaning up his own mess. (Incorrect).

Repetition of articles. 

When two or more adjectives tell about the same noun, the article is used before only the first adjective only.

Ex: I have a black and white cat. ( means a cat that is partly black and partly white)

Ex: I have a black and a white cat. (this means I have two cats one is  black and one is white)