This Spanish Easy Review grammar quiz takes a look at the indefinite articles - a, an and some. In the Spanish Easy Review quiz titled Using the Spanish Definite Article - 'The', you learned that there are four different forms of that word. Those forms were based on the gender of the word and on whether the word was attached to or describing a singular word or a plural word. That made the word 'the' an adjective. This same principle holds true for the indefinite article.
In English, the indefinite articles are a, an and some.