Use “a” before a singular countable noun that begins with a consonant sound, such as “a cat.”
Use “a” to refer to one unspecified person or thing, such as “I saw a bird.”
Use “a” before words that start with a vowel letter but a consonant sound, such as “a university.”
Use “a” in expressions of quantity, such as “a few apples.”
Use “a” in sentences like “She wants a new phone.”
Use “a” when introducing someone or something for the first time, such as “There is a man at the door.”
Use “a” with jobs or roles, such as “He is a teacher.”
Use “a” in fixed phrases, such as “once a week.”