In English, a mass noun is a type of noun that has a singular, but no plural form. 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:
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 laundromat or 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. In American English though, "less" is considered as acceptable as "fewer" to describe count nouns and is used more commonly.
A mass noun can be preceded by a count noun, as in "ten pieces of furniture" or "a gallon of water".
The word "data" is often used as a mass noun, especially by people who work with computers. In formal writing it retains its original grammatical role as the plural of "datum".
There is a certain tendency in colloquial American English to treat some mass nouns as countable, e.g. "softwares" for "software", "behaviors" for "behavior", "accommodations" for "accommodation".