* 'A', 'An' and 'The' are called Articles.
* 'A' and 'And' are called Indefinite Articles because they do not refer to any particular person or thing.
Eg: A boy. (May be any boy).
An egg. (May be any egg).
* 'The' is called Definite Article because it does refer to a particular place or thing.
Eg: The boy. (Means the boy of whom something is spoken of)
* Uses of 'A':-
i) Before a word that begins with a consonant. Eg: A pen, A school, etc.
ii) Before a word beginning with a vowel that sounds 'you'. Eg: A unit, A university, A European, etc.
iii) Before a word that begins with 'O' and sounds 'wa'. Eg: A one-legged man, A one rupee note, etc.
* Uses of 'An':-
i) Before a word beginning with vowel. Eg: An eagle, An ostrich, An ass, etc.
ii) Before a word beginning with a consonant but sounds like a vowel. Eg: An hour, An M.P, An S.D.O, etc
* Uses of 'The':-
i) Before The names of rivers (the Brahmaputra), gulfs (the Persian Gulf), seas (the Arabian Sea), mountain ranges (the Alps), newspapers (the Anandabazar Patrika), names of the countries with plural notion (the U.S.A), names of holy books (the Bible), names of important events and noted public places (the Green Revolution, the High Court), the names of train, plane and spacecraft (the Rajdhani Express, The Skylab).
ii) Before singular noun having only one existence. Eg: The earth, the moon etc.
iii) Before singular common noun to represent the whole class. Eg: The tiger eats flesh; the camel is called the ship of the desert, etc.
iv) To refer a known person or thing. Eg: Come inside the room, I like the boy, etc.
v) Before superlative degree. Eg: This is the most beautiful bird I have ever seen, He is the tallest boy in the class, etc.
vi) Before nouns preceded by adjectives. Eg: The hungry man, the sweet baby, etc.
vii) Before Ordinal numbers written in letters and not in Roman Notation. Eg: The First, the second, etc.
viii) Before plural names of families. Eg: The Roys, the Banerjees, etc.
ix) Before Proper, Material and Abstract noun to make it common. Eg: He is the Sachin of our team; Rohan is the Michel Jackson of our school, etc.
* Omission of Articles:-
i) Before Proper, Material and Abstract noun, except when they are particularized. Eg: Diamond (but, the American diamond), happiness (but, the happiness of the boy), etc.
ii) Before Plural common noun, except when they are particularized.
Eg: Tigers are carnivorous, the parrots of the zoo, etc.
iii) Before the words like school, church, hospital, college, court, etc. No article is used before them when we think of the use of the places.
Eg: Rajan goes to school (to study).
Rajan goes to the school (not to learn but to see the place).