1 Definite and Indifinite articles
Indefinite articles: a, an, some
Definite article: the
2 a and the
Did you see a moive last night? Yes I saw a comedy.
Did you see the moive last night? Yes it was excellent.
Note the difference between "a" and "the." When the first speaker uses "a," she is talking about any movie, not a specific movie. When she uses "the," she is talking about a specific movie that her listener is already familiar with.
3 Indefinite articles: a, an, some
① A
We need to hire a new salesperson.
Use "a" or "an" with indefinite nouns that are singular and countable. A noun is indefinite when you or your listener is not thinking of a specific person or thing. In this sentence, the speaker needs to hire someone, but he doesn‘t have anyone specific in mind. "Salesperson" is singular and countable.
I went to a moive last night.
The moive starred two of my favorite actors.
Use an indefinite article--"a," "an," or "some"--the first time you mention something. After the first mention, it becomes definite and you should use "the". In this example, the speaker uses "a" the first time she mentions "movie". After the first mention, she uses "the."
② An
a dollar an employee
a salary an umbrella
a university an honest person
Use "a" before consonant sounds and "an" before vowel sounds. Note that the sound, not the spelling, is important. "University" is spelled with a vowel, "u," but it begins with a consonant-sound, "y," so "a" is used. "Honest" is spelled with a consonant, "h," but it begins with a vowel-sound, "a," so "an" is used.
③ Some
I bought some vegetables.
I bought some meat.
How much did you buy?
Use "some" with indefinite nouns that are plural or uncountable. In this dialogue, the listener doesn‘t know specifically how many vegetables or how much meat the speaker bought. "Vegetables" is plural and "meat" is uncountable.
4 Definite article: the
I spoke to the chairman yesterday.
Use "the" with definite nouns. A noun is definite when you and your listener both know which person or thing you are talking about. In this sentence, both people know which chairman they‘re discussing. They‘ve talked about that person before.
Did you see the moon last night?
I‘d like to order the roast beef.
Use "the" with unique nouns. A noun is unique when there is only one. In these sentences, there is only one moon above the earth, and there is only one roast beef dish on the menu.