The indefinite article is used when you are speaking generally about an item. "I saw a car." "I saw an elephant." As opposed to "the" which is definite or specific. "I saw the car." It is assumed that both speaker and listener know exactly which car he is talking about. In deciding which one to use "a" or "an" you must listen to the word that follows it. If it sounds like a vowel, then you would use "an": "an elephant" If it sounds like a consonant then you would use "a": "a car" If the first letter of the following word is a vowel or a consonant, it may not help you in choosing the correct form of the article. For example, herb: In Britain the "h" is not silent and you would pronounce it like you would any other "h" word. Since the sound if the word is a consonant. you would use "a": A herb. However, in the USA, the "h" is silent in the word herb so the sound is not consonant but vocal and you would use "an": An herb. The "u" is considered a vowel but when it appears at the beginning of some words, the sound it makes is considered consonant. umbrella - the sound is vocal: an umbrella uniform - the sound is consonant: a uniform Some people use the "an" form in all words that start with "h" but honestly, it sounds a bit forced. Not enough people do this, in my opinion, to warrant making the effort.

we use ( a ) before a word that begin with correct sound , while (an) use before a word that begin a vowels sound

"an" is placed before vowels and silent "h"

you should use "a" when the first letter of the word has a consonant sound, Ex: this is a car And "an" when the first letter of the word has a vowel sound. Ex: this is an unbruella.