An article is a word that is used with a noun to indicate the type of reference being made by the noun. Articles specify grammatical definiteness of the noun, in some languages extending to volume or numerical scope. It makes noun particular or imparticular.
Indefinite Articles (a/ an)
If ‘a/ an’ is used before any noun, it represents whole race. Example: A fox is clever. (It means all the foxes are clever.)
But if we use ‘the’ before any noun, it shows a particular thing only. Example: The fox is clever. (It means some particular fox is only clever, not all)
If there is countable noun, singular number, article ‘a/ an’ is compulsorily used. Example: This is a book.
‘A/ an’ is used instead of preposition ‘on’. Example: He went on hunting. He went a hunting.
Article ‘a/ an’ is used instead of ‘any’. Example: A king ruled over a country.
‘A’ is used instead of number one. Example: I have a pen.
Article ‘a’ is used of instead ‘like’. Example: Ramesh is a ‘Devkota’ of our class. (Before proper noun, article is not used but to show like it may be used or to make particular article can be used.)
If a countable noun begins with consonant, ‘a’ is used and if it begins with vowel, then ‘an’ is used. But in some cases, before vowel or consonant ‘a/ an’ can’t be used. It is because if vowel pronounced as consonant then instead of ‘a’, ‘an’ is used. Similarly, if consonant sound is pronounced like vowel, then ‘an’ is used. Example: an hour a European a University
If short forms of word have vowel pronunciation, then ‘an’ is used and if consonant pronunciation, then ‘a’ is used. Example: a B.A. an MBBS an FRCS an MP
Before any countable noun, if there is adjective and if noun has consonant sound or vowel sound, accordingly ‘a/ an’ is used. Example: He is a great poet. He is an great engineer.
If there is bad/ good adjective, before countable noun and if before that ‘very’ is used then ‘a’ is used. Example: He is a very good student.
Before certain numerical expression, article ‘a’ is used. Example: a school a couple a hundred a dozen a great deal a lot of a number of etc.
Before certain collective nouns, article ‘a’ is used. Example: a crowd of people a bunch of keys a bouquet of flowers a bundle of sticks a chain of mountains a flock of sheep a herd of cattle
Before certain phrases, article ‘a/an’ is used. Example: a bit a little a handful of a drop of as a result in a fix in a body