Mass noun

In English, a mass noun has no plural form, only singular. Contrast this with count nouns, which denote "things". A noun phrase can refer to one or more of these things. A mass noun denotes stuff, or a substance. Stuff, unlike things, is considered to be "divisible". One speaks of removing some stuff from, say, a container. One does not normally speak of a stuff.

Some illustrative examples of English mass nouns:

water
furniture
meat
knowledge

Some nouns can have both mass noun and count noun meanings. For example, "laundry" as a mass noun is the stuff you put in the washing machine, i.e. dirty clothes. A "laundry" as a count noun is an establishment which washes clothes, also known as a laundrette. The difference in meaning can be interpreted from whether the item is counted:

"There is laundry on my street." ( must be a mass noun )
"There is a laundry on my street." ( must be a count noun )

This difference is subtle when phrased in the negative:

"There is no laundry on campus."  ( could be either )
"There are no laundries on campus." ( must be a count noun )

Another marker of difference between mass and count nouns is "less" and "fewer":

We have less furniture. We have fewer chairs.

Many English speakers incorrectly use "less" for both types; in the 1990s several British supermarkets were criticised for their signs above checkouts reading "10 items or less". The correct form is "10 items or fewer": "items" is a count noun, and a mass noun cannot be given a number anyway.

A mass noun can be preceded by a count noun: for example "10 pieces of furniture".

The word "data" is often used as a mass noun, especially by people who work with computers, but this usage is still controversial. In formal writing it retains its original grammatical role as the plural of "datum".