Use of “A”  and “AN”:

‘A’ is used before words beginning with Consonants

A boy, a girl, a horse, a room, a hockey stick, a year

A is also used before such vowels as to give the sound of consonants

A useful article; a European; a unanimous decision, a Diversity professor; such a one; a one rupee note-eyed man

‘An’ is used before words beginning with vowels and the silent ‘h’.

An hour, an honest man, an apple, an inkpot, an eye, an egg

Jamil is an honest boy. He came an hour late. This was an apple of discord among the brothers