What is a Countable Noun?

The English language contains countless nuances and subtleties, making it a difficult language to learn for non-native speakers. One stumbling block is the countable noun and its distinction from mass nouns. A countable noun is, generally, a noun that has both a singular and a plural form, as opposed to a mass noun which has no distinction of number. While this definition seems straightforward, the distinction between a countable noun and a mass noun can become blurred when exceptions to the rule occur.

An example of a countable noun is as follows:

--John has a bike. --John has two bikes.

Notice that the addition of the number "two" changes the form of the noun from "bike" to "bikes." The first noun is singular, while the second one is plural.

Here is an example of a mass noun:

--The bin is full of garbage.
--The bin is full of lots of garbage.

Notice the noun "garbage" did not change, despite the addition of the word "lots," indicating more than one. In other words, it would be incorrect to say:

--The bin is full of lots of garbages.

The mass noun in this case cannot be changed by a singular or plural form, nor does the number or amount change the noun's form. A countable noun will change under these circumstances, thereby distinguishing itself from a mass noun.

Here are a few more examples:

(countable noun)--I am wearing a tie.
(countable noun)--We are all wearing ties.

The noun is tie; it is changed to "ties" when the subject is pluralized. It would be incorrect to say "We are all wearing tie."

(mass noun)--The mail just arrived.
(mass noun)--All of the mail just arrived.

The noun is "mail;" it remains "mail" even though the determiner "All" has been added. It would be incorrect to say "All of the mails just arrived."

There are exceptions to this rule, however. For example, the word "air" is a mass noun that does not change when modified by number. For example:

--I breathed in the air.
--I could not breathe much air from that tube.