INDEFINITE ARTICLES: a / an

1. This is used when the person or thing spoken of is not definite, specific, distinct, or unambiguous.

• • • A cow (= any cow)
    • An apple (= any apple)

2. In its original numerical sense of one:

• • • Twelve inches make a foot. (But note, we say, “There are twelve inches to the foot”)
    • Not a word was said.
    • A word to the wise
    • A bird in hand is better than two in the bush.

3. in the vague sense of a certain:

• • • A Kishore Kumar (= a certain person named Kishore Kumar) is suspected by the police.
    • One evening a beggar came to my door.

4. In the sense of any to single out a member to represent the whole class:

• • • A student should obey the teacher.
    • A cow is a useful animal.
    • A teacher has the moral duty of educating his student

5. To make a common noun of a proper noun:

• • • The Principal thought himself to be a Daniel come to judgement (A Daniel = A very wise man)