Sentence Combination

You have four options for combining two complete sentences:
  1. comma and a conjunction ("and," "but," "or," "for," or "yet")
  2. semicolon and a transitional adverb, like "therefore," "moreover," or "thus"
  3. semicolon (;)
  4. colon (:)

The appropriate option(s) depend upon the context.

1. Comma + Conjunction

When combining two complete sentences with a conjunction ("and," "but," "or," "for," or "yet"), precede the conjunction with a comma.

Example: Still, the sun is slowly getting brighter and hotter, and it will eventually enter the red giant phase.

2. Semicolon + Transitional Adverb

Transitional adverbs can connect and transition between two complete sentences. They include words like the following:

  • therefore
  • however
  • moreover
  • thus
  • meanwhile
  • thereafter
  • indeed
  • instead
  • consequently
  • eventually
  • finally
  • still
  • besides

Precede the transitional adverb with a semicolon and follow it with a comma.

Example: These texts were used personally by the researcher; thus, these books were purchased at different stages of her learning process.

3. Semicolon

Semicolons can combine two complete sentences (without a conjunction) when the sentences are closely related and it would make sense to combine the sentences with "and."

Example: The chapter ends as soon as Jimmy’s love does; in the next chapter titled “Love,” the war has ended, and Jimmy has gone back to loving Martha.

4. Colon

Colons connect two complete sentences when the second sentence completes, explains, or illustrates the idea in the first sentence.

Example: A fully prescriptive approach may be harmful in this type of situation: prescriptive language could keep readers abiding by and enforcing prescriptive rules in all contexts to avoid being “wrong,” “unprofessional,” or “illogical,” even when there is no such risk.

Proofreading Tips

Locate the boundary between two separate sentences by reading each out loud. Each sentence should have its own subject and verb and be able to stand on its own.

  • Mark the boundary with a line, if you're proofreading on paper.
  • Double-check that the boundary contains the appropriate punctuation and transition words.

If two complete sentences appear next to each other without separating punctuation and/or a connecting word, they are called run-ons. You have three ways to fix a run-on sentence:

Example: The Great Red Spot is a giant hurricane on Jupiter | it has existed for over 400 years.

1. Add a conjunction and a comma.

Example: The Great Red Spot is a giant hurricane on Jupiter, and it has existed for over 400 years.

2. Insert a semicolon (;), if it makes sense to combine the sentences with "and."

Example: The Great Red Spot is a giant hurricane on Jupiter; it has existed for over 400 years.

3. Insert a period and make two separate sentences.

Example: The Great Red Spot is a giant hurricane on Jupiter. It has existed for over 400 years.

If two complete sentences appear next to each other and are only combined by a comma, they are called comma splices. You have three ways to fix a comma splice:

Example: Many children played on the Dickinson property, | Emily was often on their side against the adult order.

1. Add “and” or another conjunction after the comma.

Example: Many children played on the Dickinson property, and Emily was often on their side against the adult order.

2. Replace the comma with a semicolon (;).

Example: Many children played on the Dickinson property; Emily was often on their side against the adult order.

3. Replace the comma with a period and making two separate sentences.

Example: Many children played on the Dickinson property. Emily was often on their side against the adult order.