Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Main and subordinate clauses

We then consider the characteristics of main clauses and subordinate clauses

(295–296). Main clauses are not dependent on any other clauses and can form

sentences on their own. Subordinate clauses are dependent on other clauses and

can only form sentences by combining with main clauses. Main clauses are in

bold:

It hasn’t lasted very long.

(one main clause, also one sentence)

I’ll see you when I get back, then.

(main clause and time adverbial clause)

Will you be at home if I ring you tonight?

(main clause and conditional clause)

The guy who came this morning was very polite.

(main clause and embedded relative clause)

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Push it right down, as far as it’ll go.

(main clause and comparative clause)

Working all day like that 

you’ll exhaust yourself.

(non-finite -ing form conditional clause and main clause)