
Examples:
An orange, an elephant, an egg, etc.
Exception:
Article 'an' is used before nouns which begin with a consonant when written but make a vowel sound when spoken.
Examples:
An hour, an heir, an honest person, etc.
(These nouns begin with a vowel sound as the sound of 'h' is silent.)
An MLA, an MP, etc.
(These nouns begin with a vowel sound 'em')