A. Countable and uncountable nouns

When we use a countable noun we are thinking of specific things that can be counted (e.g. two glasses). When we use an uncountable noun we are thinking of stuff or material or the idea of a thing in general (e.g. this door is made of glass).

stuff/materials	things
glass cloth fish work	a glass / glasses a cloth a fish a work

Be careful - there's broken glass on the road. I need a cloth to wipe the table. We had fish for dinner. Hamlet is one of Shakespeare's most famous works.

Here are some more nouns that can be used in both ways with different meanings.

countable	uncountable
There's a black hair in my soup; it must be yours!	She has beautiful red hair.
Did you buy a paper this morning? [a newspaper]	The printer has run out of paper.
They are campaigning to help indigenous peoples of South America.	I love meeting people from different countries. [individuals]
Can I borrow your iron? My shirt is a bit creased. [instrument]	People used to think ships made of iron would sink. [metal]
I had some interesting experiences during my trip to Latin America. [things that happened to me]	She has little work experience. [knowledge or skill obtained from doing something]
The city has a yearly arts festival. [music, theatre, etc.]	Have you been to the modern art museum? It's wonderful. [usually refers to painting, drawing and sculpture]
He studied arts not sciences at uni. [subjects such as languages or history; always plural and without the]
I've seen that film three times. [occasions]	Time passes very slowly if you have a boring job. [clock time, calendar time]

B. Food

The names of food items often have a different meaning depending on whether they are used as countable or uncountable nouns (see fish above).