Uncountable nouns are the names of masses, materials or abstract qualities that cannot be counted and that don't have a plural form. We don't usually use a or an with uncountable nouns.
Some nouns can be used as countable and uncountable nouns, but usually with different meanings. Compare:
2. Countable and uncountable nouns.
Choose the correct option to complete the sentences.
For more information about determiners see the Grammar Reference.
For more information about countable and uncountable nouns see the Grammar Reference.