No article with plural and uncountable nouns

a/an not used

Plural and uncountable nouns (e.g. cats, wool (see here) cannot normally be used with a/an (because a/an has a similar meaning to ‘one’). Instead, we most often use no article.

• There were cats in every room. (not … a cats …)
• Doctors generally work long hours.
• Her coat is made of pure wool.
• He’s got very big ears.
• ‘What’s that?’ ‘I think it’s salt.’

Confusing nouns

Some nouns that are countable in some other languages are uncountable in English (see here) for a list).

• I need information and advice. (not … an information and an advice)
• You’ve made very good progress. (not … a very good progress.)

And note that we never use a/an with weather or English.

• We’re having terrible weather. (not … a terrible weather.)
• She speaks very good English. (not … a very good English.)

some and any

Instead of no article, we can sometimes use some or any.

• We met some nice Danish girls in Scotland.
• Have you got any matches?

For details, (see here).

the

Instead of no article, we use the when we want to say ‘You and I both know which I mean’ (see here). Compare:

• I’m working with children. (The hearer doesn’t know which ones.)
  How are the children? (= the hearer’s children)
• We need salt. (= any salt)
  Could you pass the salt? (The hearer can see the salt that is wanted.)

But we usually use no article, not the, to talk about people, things, etc in general (see here).

• Are dogs more intelligent than cats? (not … the dogs … the cats)
• Everybody likes music. (not … the music.)

note

For expressions like a coffee, a knowledge of Spanish, (see here), (see here).