A1
Articles (a, an, the)
Articles tell you whether a noun is indefinite or definite. Many languages have no articles, so this is new grammar, not a translation of a Ukrainian or Polish word.
A / An — indefinite
Use with a singular countable noun when you mention something for the first time, or one of many.
Choose a or an by sound, not by spelling:
a book,a cara university— [juː], a consonant sounda one-way street— [w]an apple,an hour— silenthan honest man
I saw a dog.— some dog, not identified yetShe is a teacher.What a beautiful day!
The — definite
Both speakers know which one: already mentioned, unique in the situation, or unique in general.
I saw a dog. The dog was black.the sun,the moonthe United KingdomPlease close the door.— the door here
No article: most names of people and countries (Poland), uncountables in a general sense (I like music), plurals in a general sense (Dogs are friendly).