Punctuation of Compound and Complex Sentences


A sentence having two or more main or independent clauses (MC).

A. Two or more main clauses may be joined with a semicolon (;).MC; MC.

Carl Sagan likes stars; his TV series revealed that to many Americans.

B. Two or more main clauses may be joined with a semicolon followed by a conjunctive adverb* (CA). Ordinarily, a comma will be placed after the conjunctive adverb. (MC; CA, MC.)

Carl Sagan says the same basic elements are in every object in the universe; consequently, we are star stuff.

*These are some common conjunctive adverbs (CA): accordingly, furthermore, namely, also, hence, nevertheless, anyhow, however, anyway, indeed, still, besides, likewise, then, consequently, moreover, therefore

C. Two or more main clauses may be joined with a comma followed by a coordinate conjunction (CC). MC, CC*MC.

Astronomy has been a branch of physics, but it requires much specialization.

*These are some common coordinate conjunctions (CC): for, and, nor, but, or,  yet, so (Remember these with the mnemonic word FANBOYS)


A sentence having one main clause and one or more subordinate clauses. (SC)

A. If a subordinate clause is placed before a main clause, it is set off with a comma. (SC, MC).

When a spaceship was sent to Saturn, astronomers discovered a new moon.

B. A comma is usually not needed in a complex sentence when the subordinate clause is at the end. (MC SC).

More money is needed if additional space research is to be done.

Subordinate clauses are clauses which are preceded by a subordinating word. These are some of the most common subordinate conjunctions: (SC)


Time:     when, while since, before, after, until, as soon as, as long as, now that, by the time, once

Place:    where, wherever

Cause:   because, since, as now, that whereas, inasmuch as, as long as, on account of the fact that, owing to the fact that, due to the fact that

Condition:  if, unless, on condition that, provided, providing, in the event that, whether … or not, in case that

Contrast: although, though, even though, even if, in spite of, despite, notwithstanding, while, where, whereas

Purpose: so that, that, in order that

Manner: as if, as though


who, whom, whose, which, that

Copyright (C)1999 by Ed Reber. All rights reserved.This document may be distributed as long as it is done entirely with all attributions to organizations and authors. Commercial distribution is strictly prohibited. Portions of this document may be copyrighted by other organizations.