Articles a/an

1. "a-an" are considered indefinite articles and they are used to introduce new concepts into a discourse.

1.1. Use “a”, “and” only with singular nouns

1.2. E.g. with "a" It´s a book

1.3. E.g. with "a" It´s a sharpener

1.4. E.g. with "a" It´s a pencil

2. In English, almost all words beginning with vowels will be preceded by an article.

2.1. Use “an” with words that start with a vowel sound

2.2. E.g. with "an" an elephant

2.3. E.g. with "an" an ant

2.4. E.g. with "an" an alligator

3. A/an