The correct use of articles is one of the most difficult points in English grammar. Changing one article for another, or leaving one out, can cause misunderstanding. For example, if you say ‘I like English’ you mean ‘The English Language’ but if you say ‘I like the English’, you mean ‘the English people’. See how much difference the simple word makes! Here we have three typical words ‘the’, ‘a’, ‘an’ called articles.

The is called the Definite Article because it refers to a particular person, place or thing.
Ex: Give me the brown book.

A or an is called the Indefinite Article because it leaves indefinite the person, place or thing referred to.
Ex: Give me a brown book.
Give me an umbrella.

We use ‘a’ before:
1) A word beginning with a consonant sound:
Ex: A boy, a girl, a man, a woman, a cat, a dog, a horse, a pen.

2) A word beginning with a vowel which has a Y (yoo - consonant) sound.
Ex: a union, a useful article, a uniform, a European, a eulogy (high praise),  a ewe (female sheep) etc.,

3) A word beginning with a vowel which has a W (consonant) sound.
Ex: A one rupee note, a one eyed beggar, a one-sided argument, a one-way
road etc.

We use ‘an’ before:
1) A word beginning with a vowel which doesn’t have a Y or W sound.
Ex: an orange, an umbrella, an urgent piece of work, an inn, an eel, an apple, an urn.

2) A silent ‘h’: an hour, an honor, an hotel (‘h’ followed by an unstressed syllable and ‘a’ before the stressed syllable - a hall), an heir, an historical novel (but a history lesson).

3) A consonant in an abbreviation which begins with a vowel sound
Ex: an M.A., an M.Sc., an M.P., an ‘L’ board, an S.I., but a B.A., a B.Sc.,

The use of the Indefinite Article
The Indefinite Article is used
1. In its original meaning of one:
Ex: There are three feet in a yard.
It needs a hundred rupees.
Not a hair of his head can be touched.

2. In the sense of a certain:
Ex: I met a magician last week.
An uncle of yours asked about you.
A book was taken by the boy.
A train was on the platform.

3. Before a common noun in the singular to denote a class:
Ex: A tiger is fierce (all tigers).
A cow is a holy animal (all cows).
A rose is a beautiful flower (all roses).
A dog is faithful (all dogs).

4. In the sense of the same:
Ex: Birds of a feather flock together.
They were of a size.
Our shirts are of a size.

5. Before a name to indicate that the person is known to the speaker by name only:
Ex: A Mr. Smith is on line.
A Miss Lily has come for you, dad.
(A Mr. Smith means ‘a man called Smith’ and implies that he is a stranger to the speaker. ‘Mr. Smith’ without a, implies that the speaker knows Mr. Smith or knows of his existence).

6. With a proper noun used as a common noun:
Ex: He thinks he is a Napoleon. (a great general)
A Daniel has come to judgment. (a wise and upright judge)

7. Before the name of a profession, a trade, an occupation, a class, and a religion:
Ex: a clerk, a doctor, a lawyer, a teacher, a farmer, a Hindu, a Muslim.

8. Before the numbers, dozen, score, gross, hundred, thousand and million:
Ex: I ordered a thousand sheets of paper. She bought a dozen pencils.

9. With plurals used as singulars:
Ex: an amends, a means, an innings, a gallows, a barracks, a shambles, but news.

10. In expressions of price, speed, ratio, etc., where it means ‘every’:
Ex: a rupee, a dozen, sixty miles an hour, four times a day.

11. In exclamations before singular, countable nouns:
Ex: What a hot day!, What a pretty girl!, Such a pity!

12. To avoid ambiguity:
Ex: A black and a white kitten (Two kittens, one white and the other black).
A black and white kitten (one kitten, whose colours are black and white).

13. In apposition phrases, where the noun is being explained:
Ex: Tagore an Indian poet wrote ‘Gitanjali’.

14. With few and little in a positive sense. These adjectives are used without the indefinite article in a negative sense:
Ex: My brother has a few friends (some).
My brother has few friends. (Not many).
I have a little time (some).
I have little time. (Not much).

15. In certain phrases before singular nouns:
Ex: I have seen many an accident.
He dislikes such a statement.

The use of the Definite Article
The Definite Article ‘the’ is used
1. To point out a thing known or already referred to:
Ex: One night a wolf fell in with a dog.
The goat was all skin and bones, while the dog was as fat as he could be.

2. Before nouns of which there is only one:
Ex: the sun, the moon, the sea, the ocean, the earth, the sky, the world.

3. Before a noun which, by reason of locality, can represent only one particular thing:
Ex: Mary is in the garden (i.e., the garden of this house).
He was ill and sent for the doctor (i.e., his own doctor)

4. Before a common noun made definite by the addition of a phrase or clauses:
Ex: The boy who won the race.
The man on the donkey.
The book that I bought.

5. Before a singular noun which stands for a whole class:
Ex: The lion is ferocious (lions’ as a class).
The cow is sacred to the Hindus (cows as a class).

6. Before superlative use as nouns:
Ex: This is the most any man can do.
It is the worst for a long time.

7. Before a superlative adjective if the adjective qualifies a noun directly or (it is) followed by of:
Ex: Everest is the highest mountain in the world.
Sita is the shortest girl in the class.
We are the best of friends.

8. Before adjectives used as nouns to express an abstract idea or a quality:
Ex: The good lives on after a man has died.
A poet is constantly searching for the beautiful in life.

9. Before adjectives used as nouns to denote a whole class:
Ex: The rich should help the poor.
This adventure is for the young.

10. Before ordinal numbers in titles:
Ex: Pope John the twenty first
King George the sixth.

11. Before common nouns followed by a proper noun:
Ex: The River Godavari is in spate.
The novel ‘War and Peace’ is a master-piece.

12. Before a proper noun when it is used as a common noun:
Ex: Kalidasa is the Shakespeare of India (the greatest dramatist).
Bombay is the Manchester of India (the biggest cloth-producing centre).

13. Before a proper noun only when it is qualified by an adjective:
Ex: The great Shivaji.
The immortal Shakespeare.
The wise Solomon.
The famous Napoleon.

14. Before the names of certain well-known books:
Ex: The Vedas, The Bible, The Koran, The Ramayana.

15. Before the names of musical instruments in such contexts as the following:
Ex: He plays the violin, but I play the trumpet. Do you play the piano?

16. Before trades and professions following a proper noun:
Ex: Byron, the Poet
Newton, the Scientist
Dr. Hero, the eminent Surgeon.

17. Before plural proper names:
Ex: the Johnsons; the Smiths; the Tagores.

18. Before the names of ships, trains, aero planes, rockets, etc.:
Ex: the Golden Arrow; the Vaijayanti; the Gnat; the Krishna Express.

19. Before the names of shops, hotels, inns, restaurants, theatres, clubs:
Ex: the Savoy; the King’s Restaurant; the Princess Theatre; The Lion’s Club; the Astro Hotel.

20. before the names of gulfs, rivers, seas, oceans, chains of mountains, groups of islands, plural names of countries or where the type of government is mentioned, and some provinces:
Ex: The Persian Gulf, the Ganges, the Thames, the Black sea, the Red sea, the Indian Ocean, the Pacific, the Himalayas, the Alps, the Andaman, the West Indies, the Netherlands, the United Kingdom, the Indian Republic, the United Provinces, the Punjab, the Deccan.

21. Before districts when the noun which originally accompanies the proper noun has been dropped:
Ex: the Sahara (desert), the Gobi (desert), the Crimea (peninsula) etc.

22. Before countries and districts from which the adjective has been dropped:
Ex: the (Belgian) Congo, the (Anglo-Egyptian) Sudan, and the (Austrian) Tyrol.

23. When the initials are used:
Ex: the U.S.A., the U.S.S.R., the U.N., the W.H.O., the I.A.S., the U.P.S.C., the S.R.

24. Before a noun to give the force of a superlative:
Ex: This is the book on the subject. (i.e., the best book).
This is the man for the job. (i.e., the best man).

25. Adverbially in such sentences as:
Ex: the fewer, the better; the more, the merrier; the more they have, the more they want or the less they spend.

Omission of the Article
The article is not used:
1. Before proper nouns:
Ex: India is a great country.
Tagore wrote verses in Bengali.

2. Before titles followed by a proper noun:
Ex: President Kennedy was assassinated.
Doctor Hahnemann invented Homoeopathy.
Elizabeth II became Queen of England after the death of her father.

3. Before common nouns in the plural number used in a general sense:
Ex: Boys are generally naughty (general). Dogs are faithful animals (general).

4. Before common nouns in the singular number used in their widest sense:
Ex: Man is mortal.
Woman is man’s companion in life.
Science tries to discover the laws of nature.

5. Before material nouns used in a general sense:
Ex: Gold is a valuable metal (material general).
Cotton is cultivated on a large scale in India (material general).
But the gold in my ring is too soft (material-particular).

6. Before abstract nouns used in a general sense:
Ex: Wisdom is the gift of heaven (Abstract-general).
Honesty is the best policy (abstract general).
But The Wisdom of Solomon is well known (Abstract noun particularized)
The honesty of those boys is gratifying (abstract noun emphasized)

7. Before the names of sciences, etc., when they are used in a general sense:
Ex: Mathematics is a very interesting subject.
Logic is not taught in all schools.
Do you learn history at school?

8. Before superlative adjectives and adverbs used predicatively:
Ex: He knows best (adverb-superlative of ‘Swell’)
That is best (adjective-superlative of ‘good’).

9. Before a noun in the possessive case, i.e., before the person or thing possessed:
Ex: the girl’s aunt
the boy’s uncle.

10. Before a noun preceded by a possessive adjective:
Ex: my book, my pen.

11. Before places of assembly such as church, school, market, exchange, person, college, hospital, university, etc., when these places are visited for their primary purpose:
Ex: We go to school (to study), to market (to sell or buy), to church (to pray), to prison (as a punishment).
But when these places are visited for any other purpose, the article is used:
Ex: You will get a bus at the church.
I went to the school to see the headmaster.
He returned from the prison, where he had been visiting his brother.

12. In certain verbal phrases:
Ex: to catch fire; to take breath; to give battle; to send word; to give ear; to leave school; to set sail; to lose heart; to set foot; to leave home,

13. In certain prepositional phrases:
Ex: in hand, at home, in bed, in debt, at school, by day, by night, at sunrise, at sunset, at night, at interest, on earth, in heaven, by land, by sea, by train, by boat, by name, on horseback, on foot, at dinner, at table, in love, in court, for money.

14. Before names of meals, unless specially qualified:
Ex: Dinner is ready. We can talk it over at lunch, but will you bring in the tea?
(i.e., the tea we are waiting for).

15. Before names of seasons:
Ex: Winter is the best time for reading.

16. Before a few nouns denoting time, especially in connection with school life:
Ex: term, break, prayers, hall (dinner), preparation. The same applies to day, night, morning, evening dawn, twilight, dusk, when used in an abstract or general sense, and in some prepositional adjuncts: Come Ionic during break, will you? Term was drawing to a close. We always got up at dawn.

17. Before nouns like day, the names of the days of the week, night, week, month, year, preceded by next or last, except sometimes when starting from a point of time in the past or future:
Ex: I propose to meet him next Sunday. I met him at a concert last week. But: The next day she was still feeling weak and giddy.

18. Before concrete nouns like Heaven, Hell, Paradise, Parliament, and Congress:
Ex: The road to Hell is paved with good intentions. Fate had decided  otherwise.

19. Before uncle, mother, aunt, etc.:
Ex: Father is angry, Uncle is cross with us, Mother is kind.

20. Before ‘home’ when it means the home of the speaker, or the person spoken to:

Ex: Go home, Stay at home.