They precede the nouns and are used in undefined expressions.

• A/an is used only countable singular nouns.Those who start with consonant letter have "a"tag at the beginning of the word, and nouns that begin with a vowel that will have "an" tag at the beginning of the word.

• A /an is usually used when expressing what an object is.We cannot use countable singular nouns alone.

        Example

• I saw an accident of a car.

• Alex is training to be an engineer.

• That is an excellent pencil.

• I need a kilogram of salt.

. If we are talking about a specific object, "the" is used. Countable singular or plural and can be used with all uncountable nouns.

Example

• Yesterday , I bought a blouse and a skirt. The blouse was surprisingly cheap, but the skirt was more expensive.

• The movie is perfect