Run-ons and Comma Splices
What They Are and How to Fix Them

A run-on sentence, also called a fused sentence, occurs when two or more independent clauses are put together with no mark of punctuation. A comma splice is the situation with only a comma between the clauses, and a comma is not enough to join them.
(Note: An independent clause can stand alone as a separate sentence; it has a subject, a verb, and makes sense by itself as a complete thought.)

Example: Laura forgot to set her alarm she was late to work. (run-on)

Example: Laura forgot to set her alarm, she was late to work. (comma splice)

There are five ways to fix run-ons and comma splices. Which you choose depends on the sense of your sentence; there is no one best solution.

  1. Make the clauses into separate sentences.

    Laura forgot to set her alarm. She was late to work.
  2. Join the clauses with a semi-colon.

    Laura forgot to set her alarm; she was late to work.
  3. Join the clauses with a comma and a coordinating conjunction (and, but, or, not, for, so, yet).

    Laura forgot to set her alarm, so she was late to work.
  4. Join the clauses with a semi-colon, a conjunctive adverb, and a comma (see list).

    Laura forgot to set her alarm; consequently, she was late to work.
  5. Introduce one of the clauses with a subordinating conjunction (see list).
    Note that you are making the clause into a fragment – no longer can it stand alone as a separate sentence.

    Since Laura forgot to set her alarm, she was late to work.

Conjunctive Adverbs (list of the most common choices, grouped by their function):

Similarity: likewise, similarly
Contrast: however, nevertheless, on the contrary, on the other hand, otherwise
Result/Effect: accordingly, as a result, consequently, hence, therefore, thus
Addition: also, furthermore, in addition, in the first place, moreover
Emphasis/Clarity: in fact, in other words, indeed, that is
Time: afterward, later, meanwhile, subsequently
Example: for example, for instance, to illustrate

Subordinating Conjunctions (list of the most common choices, alphabetically):

after even though rather than when
although except that since whenever
as if so where
as if if only so that whereas
as long as in case that wherever
as though in order that though whether
because now that unless while
before once until  
even if provided that