A. Indefinite Article is a determiner 'a' and 'an':
a. introduces a noun phrase and implies that the thing referred to is non-specific. (e.g. I bought a book for you.)
b. Typically, the Indefinite Article is used to introduce new concepts into a discourse. (e.g. A story is a work of imagination.)
c. We do not use the Indefinite Article with plural nouns and uncountable nouns. In the plural and uncountable noun, we use the noun only (e.g. They are such hard workers. (not some ~) Water is your body's most important nutrient, is involved in every bodily function, and makes up 70- 75% of your total body weight.)
Idiom 365
Hit the sack / sheets / hay: go to bed or go to sleep.
Example: Hey Bob, you look terrible! What time did you hit the hay last night?