Uncountable nouns are nouns which cannot be counted.
A lot of nouns in English are countable, so you can say: 1 orange, 2 oranges, 1 biscuit, 5 biscuits, 1 house, 10 houses etc.
Uncountable nouns do not change their spelling and you cannot put a number (1,5,10 etc) directly before them. Here are some examples:
Accommodation, furniture,
So you cannot say: 10 accommodations, 20 furnitures etc. because the words accommodations and furnitures do not exist.
If you want to be express the number of items you are referring to, you can say: 10 types of accommodation, 20 pieces of furniture etc.
Different nouns also have certain collocations.
E.g. We say pieces of furniture. NOT pools/scores/locks of furniture etc.
Countable nouns can either be singular or plural.
E.g. Boy, boys. Girl, girls. House, houses. Child, children. Person, people.
Certain words modify plural countable nouns and certain words modify uncountable nouns and certain words can modify both plural countable nouns and uncountable nouns. This is really useful to know if you want to pass the CAE or FCE exam, you can lose marks for making mistakes here. Your knowledge of grammar is most specifically tested in the Use of English papers of these exams. We offer a B2 First course and a C1 Advanced course which help you with these and every other section of these exams.
If you don't know which exam to take, check out my FCE, CAE or IELTS page.
Plural countable nouns only – several, many, few
Uncountable nouns only – much, little
Plural countable nouns & uncountable nouns – some, lots of, a lot of
If talking about uncountable nouns when not referring to the number, English people usually refer to the item/items as singular (not as plural objects).
E.g. “This furniture is lovely”
There is more useful information about these nouns on this website.