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Crowded holiday resorts are not very pleasant

Holiday resorts which are crowded are not very pleasant

The word crowded in the first sentence is an adjective which

are crowded is a clause (it has a finite verb are) The clause is doing

exactly the same work as the adjective it is describing the holiday

resorts (or qualifying the noun holiday resorts) So we can call it an

adjectival clause or (more usually) a relative clause because it relates

to the noun, in this case by means of the word which Relative clauses

(like adjectives) can describe persons things and events

The use and omission of commas in relative clauses

There are two kinds of relative clauses in the written language

1 Relative clauses without commas (sometimes called defining restrictive or identifying) They provide essential information about the subject or object What kind of government would be popular? - The government which promises to cut taxes

2 Relative clauses with commas (sometimes called non-defining non-restrictive or non-identifying) They provide additional information which can be omitted The government which promises to cut taxes will be popular

The inclusion or omission of commas may seriously affect the meaning

of a sentence Compare

The government which promises to cut taxes will be popular The government which promises to cut taxes will be popular

The first sentence refers to any government which may come to power

in the future The second is making a statement about the popularity of

The complex sentence relative pronouns and clauses

the government that is actually in power at the moment Whatever it does this government will be popular Among other things it promises to cut taxes Alternative punctuation, such as dashes, would further emphasize the introduction of additional information

The government - which promises to cut taxes - will be popular Or we could use brackets

The government (which promises to cut taxes) will be popular In speech, a break in the intonation pattern indicates these markings e g when reading aloud or delivering a news bulletin

Not all relative clauses need be rigidly classified as defining or non-defining The inclusion or omission of commas may be at the writer's discretion when it does not result in a significant change in meaning

He asked a lot of questions () which were none of his business ()

and generally managed to annoy everybody