Write:a/an or the. An old man wants to sell the horse. He changes the horse for ... cow.

An old man wants to sell the horse. He changes the horse for a cow.

A / an and the are articles. There are two kinds of articles in English. They are definite article and indefinite article. A / an is indefinite article. The is definite article.

The meaning of a / an is one. The difference is in their use. A is used before consonants. a horse, a cow, a dog. An is used before vowels. an eagle, an apple. Indefinite article is used when noun is unknown.

Definite article is used when noun is already known.