Punctuation of Compound and Complex Sentences

  • COMPOUND: A sentence having two or more main or independent clauses (MC).
    • Two or more main clauses may be joined with a semicolon (;). MC; MC.
      • Ex: Carl Sagan likes stars; his TV series revealed that to many Americans.
    • 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.)
      • Ex: 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
    • Two or more main clauses may be joined with a comma followed by a coordinate conjunction (CC). MC, CC*MC.
      • Ex: 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)
  • COMPLEX: A sentence having one main clause and one or more subordinate clauses * (SC).
    • If a subordinate clause is placed before a main clause, it is set off with a comma. (SC, MC).
      • Ex: When a spaceship was sent to Saturn, astronomers discovered a new moon.
    • A comma is usually not needed in a complex sentence when the subordinate clause is at the end. (MC SC).
      • Ex: 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