Subordinate and complement clauses

The subordinate clause in composite sentence 1 above is a complement of the verb knew. In this case, the clause is an object complement, but subject complement clauses are also possible:

That Profumo lied to Parliament caused a major scandal.

While subject complement clauses are possible in English, they are sometimes perceived as a little inelegant and can be replaced by nominalized variants in the subject NP position:

Profumo’s lying to Parliament created a major scandal.

Complement clauses may involve non-finite forms of the verb – an infinitive in the first example below and a gerund in the second:

John wants to get out.

Paul likes playing games on his mobile phone.

Present participles figure frequently in adjunct clauses, highlighting an important difference between prescriptive usage, in which they must have the same subject as the main verb, and everyday usage, which is more relaxed about a requirement of which even Shakespeare is known to have fallen foul:

Now, Hamlet, hear. ’Tis given out that, sleeping in my orchard, a serpent stung me.

As many a pedant has noted, not even the Great Bard could make serpents able to sting (bite?) in their sleep!