• if the reader has enough information to identify the noun specifically

COUNT: Please turn on the lights. We’re going to the lake tomorrow.

NONCOUNT: The food in Italy is excellent.

• if the noun refers to one item and

• if the item is singular but not specific

COUNT: Bring a pencil to class. Charles wrote an essay about his first job.

NOTE: Do not use a or an with plural or noncount nouns.

• if the noun represents an unspecified amount of something

• if the amount is more than one but not all items in a category

COUNT (plural): Amir showed us some photos of India. Many turtles return to the same nesting site each year.

NONCOUNT: We expect some rain this evening.

NOTE: Sometimes no article conveys an unspecified amount: Amir showed us photos of India.

• if the noun represents all items in its category

• if the noun represents a category in general

COUNT (plural): Students can attend the show for free.

NONCOUNT: Coal is a natural resource.