It is sometimes difficult to know which article (a, an, or the) to use in an English sentence. Here are a few rules to help:
A – We use “a” in front of singular nouns ( a person, place or thing) that we can count and that begin with a consonant sound: a pen, a pencil, a dog, a university
Why do we use “a” in front of “university” ? Even though the word “university” begins with a vowel letter, it doesn’t start with a vowel sound. The beginning of the word “university” sounds like it starts with a “y”spoken like “yuniversity”. So, we use the article “a”.
An – We use “an” in front of singular nouns that we can count and that begin with a vowel sound: an apple, an eye, an ice cream, an hour
An “hour”? “Hour” starts with a consonant! But when we say “hour”, we don’t pronounce the “h” sound, so the beginning of the word starts with a vowel sound spoken like “our”. So, we use the article “an”.
We also use a/an when we are not talking about a specific thing, but any one of a group of things:
I would like an apple.
Where is a grocery store?
We also use a/an when we are talking about a topic for the first time or when not everyone listening knows what we are talking about:
I’m going to a party tonight. Would you like to go with me?
The – We use “the” in front of a specific item we are naming.
I’d like the red apple.
Where is the Food Lion on this street?
We also use “the” when we are talking about something the second time or when everyone listening knows what we are talking about:
I’m going to the party at John’s house tonight. Are you going, too?
No article – Finally, we don’t’ use any article in front of plural nouns or nouns that we can’t count:
He eats rice.
I drink water.
She likes children.
If you’d like to practice using a, an, and the, click the following link: http://a4esl.org/q/h/grammar.html#ART