Countable nouns are individual objects, people, places and things that can be counted.
For example, books, houses, Americans, cats, dogs, cars, etc.
A countable noun can be singular (a book) or plural (two books)
The singular form of a verb is used with a singular countable noun : the apple is red.
The plural form of a verb is used with a plural countable noun : the apples are red.

Uncountable or mass nouns are substances, concepts, information, materials, etc. which are not individual objects and cannot be counted. They have no plural form.

Some examples:

Liquids and gases:milk, cream, water, coffee, smoke, air, oxygen
Solid and granular substances:bread, cheese, meat, rice, sugar, salt, sand
Materials:wood, plastic, glass, paper
Concepts/abstract ideas:hope, peace, beauty, entertainment, freedom
Feelings and qualities:joy, anger, efficiency, honesty, pride, happiness
Activities:homework, sleep, surveillance, work 

Uncountable or mass nouns are :

  • used with no indefinite article (a/an) :   Drink water if you are thirsty. (not: a water)
  • take a singular verb : Water is safe to drink in this area.

Common uncountable nouns :

advice, accommodation, baggage, bread, cheese, equipment, furniture, happiness, information, knowledge, literature, luggage, money, music, news, pasta, progress, research, sadness, travel, water, work …

Examples of use :

  • Water is a necessity.
  • Could I have a slice of bread please?
  • Have some cream with your strawberries.
  • That’s an interesting piece of information.
  • Here is the latest news.

To talk about a certain quantity, we use :
some/ a piece of/ a drop of/ a glass of/ a slice of, etc.

  • some milk / a drop of milk
  • a piece of cheese/cake/pizza
  • a slice of bread
  • a glass of water
  • a piece of advice/information/news/luggage
  • a news item

Examples of words used to quantify uncountable nouns:

A bag of flour/oats
A bar of chocolate
A bowl of rice/cereal/fruit
A carton of cream/yogurt
A clove of garlic
A cube of ice
A grain of rice
A handful of olives/nuts
A head of lettuce
A jar of jam/honey
A knob/pat of butter
A loaf of bread
A lump of sugar
A pinch of salt
A scoop of ice-cream
A slice of bread/cake
A sprig of parsley/thyme
A square of chocolate
A stalk of celery/rhubarb
A stick of cinnamon
A drop of milk/rain
A bottle of wine
A bowl of soup
A can of coke/beer
A cup of tea
A dash of lemon juice
A dose of medicine
A litre/gallon of petrol
A glass of water/wine
A jug/pitcher of water
A mouthful of coffee
A pint of milk/beer
A pot of tea
A pool of blood
A quart (2 pints) of milk
A shot of vodka
A sip of water/tea/beer
A spoonful of medicine
A thimble of whisky
A trickle of water
A bar/cake of soap
A bottle of perfume
A ball of cotton
A cloud of smoke
A coat of nail polish
A dab of perfume
A flash of lightning
A piece of news
An item of clothing
A piece of luggage
A pile of money
A ray of sunshine
A roll of toilet paper
A sheet of paper
A stick of chalk
A tube of toothpaste
A speck of dust
A stick of deodorant
A string of pearls
A stroke of luck

Plural nouns with no singular form:
Some plural nouns have no singular form.
Examples are : earnings, (reading) glasses, trousers, savings, shorts, scissors, binoculars.

These nouns take a plural verb :

  • The company’s earnings are increasing every year.
  • Our savings are kept in the bank
  • These scissors are rusty.

To refer to one item of clothing, tools or instruments which consist of two parts, a pair of is used :

  • A pair of trousers/shorts/jeans/pyjamas.
  • A pair of scissors/clippers/pliers.

Nouns ending in ‘s’ that take a singular verb:
Some nouns appear to be plural in form but take a singular verb.
For example : news, gymnastics, athletics, economics, physics, politics, series

  • Athletics is a competitive sport.
  • The news is not very good I’m afraid.
  • They say politics is a complicated business.
  • Gymnastics is fun to watch.
  • Linguistics is the study of language.
  • Physics is a difficult subject for many students.
  • The new adventure series on television is very exciting.