Lessons · Grammar/Writing
CLT Grammar/Writing · Lesson
Sentence boundaries
Two complete sentences cannot be joined with only a comma (a comma splice) or with nothing at all (a run-on), and a piece of a sentence cannot stand alone (a fragment).
- Test each side of the break: could it stand alone as a sentence, with a subject and a verb?
- Two complete sides need a period, a semicolon, or a comma plus "and," "but," "or," "so," "for," "nor" or "yet."
- If one side is incomplete, it needs a comma or no mark, never a period or semicolon.
- Words such as "however" and "therefore" do not join sentences. "; however," works; ", however," between two sentences does not.
Wrong The telescope was crude, it still showed mountains on the Moon.
Right The telescope was crude; it still showed mountains on the Moon.
Both halves are complete sentences, so a comma alone is a splice. A semicolon (or ", but it") fixes it.
- A semicolon works only where a period would. If a period would make a fragment, so does a semicolon.
- A choice can be grammatical but change the meaning with the wrong joining word ("so" instead of "but"). Check both.
Every practice question comes with a full explanation, including why each wrong choice is wrong. Free, with no account.