Countable nouns, also known as count nouns, are nouns referring to things that can be counted as individual items and have a distinct plural form. Countable nouns can be counted using numbers and specifically referred to with the indefinite articles a and an.
There will be a new student starting next month.
There will be seven new students starting next month.
I’ve only had one car.
I’ve only had three cars.
There is an ostrich at the zoo.
There are four ostriches at the zoo.
Take note that many nouns have irregular plural forms. Not all count nouns are so easily categorized by checking whether they can be made plural by adding –s according to normal spelling rules. Some nouns, such as sheep or fish, do not change at all, but they are still countable and able to take an indefinite article.
A man stopped by the shop this morning. (singular)
Three men stopped by the shop this morning. (plural)
Do you see the person in the blue uniform? (singular)
Do you see the people in the blue uniforms? (plural)
A sheep wandered off earlier. (singular)
Four sheep wandered off earlier. (plural)
There is one fish in the tank. (singular)
There are fifteen fish in the tank. (plural)
Uncountable nouns, also called non-count nouns, cannot be counted as individual objects or units or take indefinite articles.
The water at the beach was warm and clear.
The boss’s patience was running out.
The toddler spilled milk all over the floor.
Everyone was tired of hearing biased and sensationalized news delivered by buffoons on television.
Some uncountable nouns may be measured and contained but cannot be counted on their own. While units or containers may be counted, the uncountable substances they measure and contain remain uncountable.
John drank two liters of water today.
There are seven canisters of kerosene outside.
We just bought one quart of milk.
While liters, canisters, and quarts are countable units, water, kerosene, and milk remain uncountable.