There are Definite and Indefinite Articles in English grammar. "A" and "An" are called Indefinite Articles and "The" is called Definite Article.
Use of "A" in English Grammar
Article "A" is used with the words which give consonant sounds. Sometimes a word starts with vowels like o, u but it gives consonant sound then Article "A" is used also.
For Examples:
He is a one eyed man.
Here the word "one" starts with the vowel "o" but it is giving consonant sound. That's why we have used Article "A" before the word "one".
The cow is a useful animal.
Here the word "useful" starts with the vowel "u" but it is giving consonant sound. That's why we have used Article "A" before the word "useful".
I bought a book from the shop.
Here the word "book" starts with consonant "b" and it is giving consonant sound therefore Article "A" has been used.
He lives in a European Country.
He works in a University.
Use of "An" in English Grammar
Article "An" is used with the words which give vowel sounds. Sometimes a word starts with the consonants like m, s but it gives vowel sounds then Article "An" is also used.
For Examples:
He eats an apple once a day.
Here the word "apple" starts with the vowel "a" and it is giving vowel sound. Therefore Article "An" has been used.
An umbrella is very useful in the rain.
He bought an elephant yesterday.
He is an M.A. M.Ed.
Here the word "M.A." starts with the consonant "m" but it is giving vowel sound. That's why, Article "An" has been used.
He started an SIP in mutual fund.
Use of "The" in English Grammar
We use "The" before rivers, mountains, natural objects (sun, moon, stars, earth etc.) religious books, newspapers, superlative degrees etc.
For Examples:
The Ganga is a sacred river of India.
The Geeta a religious book of Hindus.
The stars are shining in the sky.
The earth moves round the sun.
I read the Tribune daily.
The Himalayas are in the north of India.
He is the best actor in Hollywood.
