NOUNS THAT DO NOT ADD 'S' IN THE PLURAL (PART 3)

Some nouns function as both countable and uncountable nouns. Here are some examples.

Air(s)
When we are talking about the mixture of nitrogen, oxygen and other gases that is all around us, we would not normally add 's'.
e.g. I'm going outside for some fresh air.
Sometimes, however, we say that someone is 'giving themselves airs', meaning that they are behaving pretentiously. In this context, it is correct to add 's'.

Buffalo(es)
Collins Dictionary states that the plural of buffalo can be either buffalo or buffaloes and both are used. A recent video on the Washington Post website uses both versions! The title is, 'Runaway buffaloes give police a hard time in Ariz', while the caption (attributed to Reuters) reads, 'Officers had a hard time subduing a herd of buffalo . . . '
The noun, deer(s) is similar to buffalo(es) in that the plural of deer can be either deer or deers.

Criticism(s)
When talking about criticism in general, we do not add 's'.
e.g. 'My blog has received a great deal of criticism.'
Someone might also say something like, 'I have a number of criticisms to make about this blog', meaning that they would like to point out several different faults with it. In this context, it is correct to add 's' in the plural.

Experience(s)
I might say, 'I have experience in proofreading scientific papers.'
A statement like this is often used to inspire confidence; it means that I have proofread a lot of papers; therefore, you can be confident that I know what I am doing and will do a good job. In this context, 's' would not be added to 'experience'.
'Experience' can also be used in a different way.
e.g. Doing a parachute jump was one of the scariest experiences of my life.
Here, 'experience' is used to refer to a particular event. In this context, it is correct to add 's' in the plural.

Friendship
If we talk about friendship in general, we would not add 's'.
e.g. 'Friendship has been given a special status in our society.'
We may also talk about individual friendships, in which case we would add 's' if we are talking about more than one of them.
e.g. 'Almost 60% of us claim that our friendships are more important to us than career, money or family.'
(The Guardian)

Hair(s)
No 's' is added when referring to a quantity of hair.
e.g. My hair is brown. (i.e. The 100,000 or so hairs I have on my head are nearly all brown.)
When talking about individual strands of hair, we add 's' to form the plural.
e.g. I pulled three grey hairs out of my fringe this morning.

Joy(s)
Joy is an uncountable noun in the following context.
'The culture of the Red Bus Project is full of joy . . .' (The Murray State News)
Here, 'joy' refers to a general feeling of happiness; however, we sometimes talk about individual 'joys'.
e.g. '. . . it takes time to realise the joys of Radio Four . . .' (What's on Stage)
Evil(s), freedom(s), grief(s), happiness(es), hope(s), sadness(es), trouble(s) and
virtue(s) function in a similar way to joy(s). 

Paper(s)
Paper can refer to paper in general, in which case we would not add 's'.
e.g. Junk mailing wastes a lot of paper.
A paper can also refer to a newspaper, or a document, such as a research paper, or a discussion paper. In this context, we would add 's' in the plural.
e.g. I have two papers which must be proofread by tomorrow. 

Sleep(s)
Sleep is normally an uncountable noun.
e.g. How much sleep do you need?
Sometimes, however, parents or carers find that children struggle to understand the concept of time. Frequently, they ask questions like, 'how long is it until Christmas Day?' An answer like, 'two weeks' is sometimes hard to understand, whereas 'fourteen sleeps' is much more straightforward. This means that, after fourteen bedtimes, it will be Christmas Day. ('Sleeps' in this context would not be used in formal writing.)

Time(s)
If we are talking about time in general, it is regarded as an uncountable noun.
e.g. I will have plenty of time to spend with my parents this weekend.
'Time' is a countable noun when it is used to mean an instance.
e.g. Please come down for lunch; I have already called you three times!

Work(s)
Work can be something that needs to be, or has been done, in which case it is an uncountable noun.
e.g. I have a lot of work to do today.
Work can also function as a countable noun, when it refers to something that someone has done or made.
e.g. 'The 10 greatest works of art ever' (The Guardian)

Water(s)
When talking about a quantity of water, we would not add 's'.
e.g. There is a lot of water in the ocean.
The phrase, 'sample the waters' is often used when talking about visiting a place where the water is thought to have health benefits.
e.g. 'Sample the waters at Taychreggan' (Highland News)

Other words that fall into this category are:

cloth(s)
culture(s)
death(s)
democracy (democracies)
fish(es)
ice(s)
insurance(s)
justice(s)
liberty (liberties)
money (monies)
music(s)
oxygen(s)
pity (pities)
poetry (poetries)
pride(s)
progress(es)
rain(s)
research(es)
sheep(s)
speed(s)
steel(s)
surveillance(s)
swine(s)
taste(s)
travel(s)
trout(s)
weather(s)


Please feel free to comment if you can think of words that I have missed, or if you disagree with any of the above.

References accessed while writing this blog post:
British Council
Business Writing
Collins English Dictionary
Count and Non-Count Nouns
Learn English Online
Learn English Today
The EF Englishtown Blog
English Plurals (Wikipedia)