The words "a", "an", and "the" are special adjectives called articles. Articles define nouns as either specific or unspecific. "The" is a definite article. Definite articles are used to refer to a specific noun or a noun that has been previously specified. They can be used before singular, plural, countable, and uncountable nouns. "The" is used before words that start with consonants or vowels. It does not matter what letter the word starts with.
Definite Articles - singular and plural nouns
Please close the door.
I am going to the storetoday.
The birdlanded on the roof.
Dinner is on the table.
The apples are sweet.
The customers are getting impatient.
Who ate all of the donuts?
The flowersare beautiful.
Definite Articles - countable and uncountable nouns