∗ If the noun begins with a consonant letter; (a) is placed in front of the noun.
∗ If the noun starts with a vowel; (an) is placed in front of the noun.
∗ Pronunciation is considered when determining the right article.
∗ (a) and (an) are never used before an adjective or adverb that exists alone; they must be completed with a noun.
∗ Nouns must be countable to use with (a) and (an).