The idea of subordination is that there are two clauses in a sentence. One is the main focus of the writer, the other only the added information. The first is called the main clause, the latter the subordinate clause. The added information may explain the noun or the verb.

Subordinate clauses that explain the noun are 'adjective clauses', which was already discussed in Unit 2.

Subordinate clauses that explain the verb are 'adverb clauses'. There are many kinds of adverb clauses.

1. Clauses of Time: when, before, after, as soon as, once, etc.

2. Clauses of Condition: if, unless

3. Clauses of Manner: as, as if and as though

4. Clauses of Reason: because

5. Clauses of Contrast: even though, although, though