A, An, The: Little words, big meaning

"A," "An," and "The" are adjectives called articles. Special usage rules apply:

• "A" and "An" are indefinite and are used with general nouns or nouns not previously mentioned. I have a cat and a dog for pets; Geri has an octopus for a pet. A man and a woman walk on a path.
• "The" refers to nouns previously mentioned. The cat and the dog don't get along. The octopus is a baby. The man took the woman's hand when the path got rocky.
• "The" is used to refer to specific nouns: The elephant is a highly intelligent animal. The Nile is found in the African continent. The sun should shine tomorrow after the storm passsed overnight.
• "A" is used before nouns that begin with a consonant or consonant sound: A history assignment, an university degree.
• "An" is used before nouns that begin with a vowel or vowel sound: An assignment, an hour.
• "A" and "An" are also used to refer to your profession: I am an admin.