Articles are divided into two groups

1. Indefinite Article : Article ‘A’ and ‘An’ come under this group.

2. Definite Article : Article ‘The’ comes in this group.

Important Rules of ‘A’ & ‘An’

1. Use of A or An is depend on the pronunciation of the word that comes just after these and not on the spelling of the word. If that word starts from vowel sound, then ‘An’ is used and if word starts from consonant sound, then ‘A’ is used.
(i) He is an honest man.
(ii) He is an SDO.
(iii) I will reach there after half an hour.
(iv) He is a one eyed man.

In above sentences honest, SDO, hour all starts from vowel sound but not with vowel so an is used while one starts with vowel but without vowel sound so a is used some more words which do not starts from vowel but an is used before them are as follows honourable, MLA, MP, MA, M Sc, SP, RTS, RTC, etc.
Some words which starts from vowel but not with vowel sound and hence ‘A’ is used before them. e.g., Union, university, uniform, useful, European, USA, Unique.

2. A and An are used before singular Countable noun , i.e., before common noun and collective noun.
(i) She is a doctor.
(ii) He is an engineer.
(iii) If an adjective or adjective + adverb come , before a noun then A or an is used according to the nearest word. .

(i) He is an intelligent boy.
(ii) He is a good boy.
Here in first sentence ‘intelligent’ (adjective) is followed by an as it starts with vowel sound while in second sentence ‘a’ comes before good (adjective) as good starts with consonant sound.

3. Normally A or An is not used before proper noun but in some cases a or an are used before proper noun It is used for telling the preposition of that particular proper noun.
e.g., He is a Buddha

Important Rules of ‘The’

1. When any singular countable noun comes first time in any speech then A or An is used but When repetition I this noun occurs then ‘the’ is used before it.
e.g., There is a knife in my kitchen. The knife is very sharp.

2. ‘The’ is used before superlative degree.
e.g., The tiger is the fastest animal.

3. ‘The’ is used before the name of directions e.g., the east, the west the north, the south.

4. ‘The’ is used before the names of the group of islands.
e.g., The Andamans, The East Indies etc.
Exception : Some islands are single so ‘The’ is not used before them.

5. ‘The’ is used before the historical books.
e.g., The Gita, The Quran etc.

6. ‘The’ is used before the name of river, Ocean, Bay, forest, desert etc.
e.g., The Ganga, The Indian Ocean, The bay of bengal, The sahara desert etc.

7, ‘The’ is used before name of newspaper, community, political party, historical event, train, ship, aeroplane etc.
e.g., The times of India, the Hindus, the Congress party, the Quit India Movement, the Rajdhani Express, the Vikrant etc.

8, ‘The’ is used before the plural names of mountain ranges, chains of mountains etc.
e.g., The Himalayas, the alps etc.

9, ‘The’ is not used before the name of countries but if the name of countries contains words like states kingdom, republic than the is used before them.
e.g., The USA, the UK, the republic of Ireland etc.

10. ‘The’ is used before the names of government departments and armed forces.
e.g., The legislative assembly, the navy, the judiciary, the air force.

11. ‘The’ is used before the name of heavenly bodies, historical buildings, nationality etc.
e.g., The earth, the sun, the Taj Mahal, the India!l etc.

12. ‘The’ is used before the name of musical instruments.
 e.g., The piano, the harmonium.

13. Dates of month are followed by ‘the’
e.g., The 4th of March.

14. When ordinal numbers are written in letter then the is used before them.

15. ‘The’ is used before a proper noun only when it is qualified by an adjective. e.g., the great Napolean.

16. ‘The’ is used before a common noun to give it the meaning of an abstract noun. e.g., The moralist in Gandhi, revolted against the injustice.

17. ‘The’ is used before an adjective when the noun represents a class of persons.
e.g., The poor can be trusted.

18. ‘The’ is used before names consisting of adjective + noun. e.g., The New forest, the High street.

19. ‘The’ is used as a adverb with a comparative. e.g., The more she gets the more she demands.

20. ‘The’ is used before the name of persons in plural. e.g., The Birlas, the Ambanis etc.

21. When any person is referred by his designation then ‘the’ is used before his designation. e.g., the Principal, the Director etc.

22. ‘The’ is used before the names of committee, club, foundation and trust etc. . e.g., the WHO, the Rotary Club, the Rajiv Gandhi Trust.

23. ‘The’ is used before comparative degree being used for selection or comparison. e.g., He is stronger of the two.

24. The’ is used when a singular noun is meant to represent a whole category. e.g., The dog is a faithful animal.

Omission of Articles

1. Before languages, subjects name, festivals and seasons no any article is used.

2. No article is used before abstract nouns. that . express qualities, feeling etc.
e.g., Honesty is the best policy.

3. Article is omitted before material nouns and common noun
(i) Gold is a very precious metal (material noun)
(ii) what kind of bird it is (common noun)

4.Article is omitted before the month, days and year
e.g., (i) On Sunday I will go for a picnic.
(ii) ‘he’ was born in October 1996.

5.Article is omitted before names of public institution such as church, school, university, prison, hospital, court etc.
e.g., He goes to college every day.

6.Article is omitted before names of languages, colours, games and professions.
(i) Engineering is a useful Carrier.
(ii) lie is learning English.
(iii)He likes to play cricket.

7.Article is omitted before certain titles (such as emperor Ashoka, Dewan Bahadur) and names indicating the relationship.
e.g., Rahul Gandhi is Rajiv Gandhi’s son.

8.Article is omitted before names of disease like fever, cholera, small pose etc. But if disease is in plural article is used before them.
e.g. the plague, the measles, the mumps etc.

9. No article is used before regular meals such as breakfast, lunch, dinner etc.

10. No article is used before food e.g., bread, butter, cheese etc.

11. No article is used with the names of airlines, companies etc.
Eg. Indian Airlines, song etc.