Grammar - The Indefinite Articles - A and An

The Indefinite Articles: A and An
The indefinite articles a and an are used with singular nouns. Use a before most nouns or adjectives that begin with a consonant. Use an before most nouns or adjectives that begin with a vowel.

a cup                               a ball                         a class                                 a bug
an empty cup          an orange ball          an English class                       an ugly bug

an egg                      an idea                       an owl                               an accident
a brown egg            a good idea             a white owl                      a bad accident


Use a before nouns or adjectives that begin with a pronounced h, but use an before nouns or adjectives when the h is not pronounced.
a house                 a horse                      a hammer                      a hurricane
an honor               an hour                      an heir                    an honest mistake

Use a before nouns or adjectives if the vowel is pronounced as a consonant.
The following words are pronounced with a y sound.
a union                a university                     a uniform                a utensil

The following words are pronounced with a w sound.
a one-hour class                      a once-in-a-lifetime opportunity