Period (Full Stop), Semicolon, or Comma before "However"?

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The Quick Answer
Writers often ask whether they should use a period (full stop), a semicolon, or a comma before a word like "however"?

Words or phrases like "however," "as a result," "consequently" (called conjunctive adverbs) are usually capitalized and start new sentences. However, if you would like a smoother transition between your two sentences, you can use a semicolon before your conjunctive adverb.
  • I asked Tom. However, I'm not convinced he knows.
  • I asked Tom; however, I'm not convinced he knows.
You cannot use a comma.
  • I asked Tom, however, I'm not convinced he knows.
comma or semicolon before however
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Punctuation before Words Like "However"

The word "however" is often used as a bridge between two sentences. For example:
  • I love seafood. However, I can't eat shellfish.
When "however" is used like this, it is called a "transitional phrase" or a conjunctive adverb. Other common transitional phrases are "consequently," "subsequently," "therefore," and "as a result."

Read more about conjunctive adverbs.

Do Not Use a Comma before "However"

When "however" is used as a transitional phrase, there is always a comma after it but never before.
  • I missed the early plane, however, I still made the meeting.

Use a Period (Full Stop) or a Semicolon before "However"

A transitional phrase like "however" will usually start a new sentence, but if you would like a smoother transition than that afforded by a period, you can use a semicolon before it to merge the new sentence with the previous one.

Here are some examples (transitional phrases shaded):
  • I missed the early plane. However, I still made the meeting.
    • (Most of the time, your transitional phrase should start a new sentence.)
  • I missed the early plane; however, I still made the meeting.
    • (Occasionally, you can use a semicolon to create a smoother transition between your "sentences." NB: They are now independent clauses not sentences.)
Here are more examples:
  • Everyone knows he is guilty. Of course, it will never be proved.
  • Everyone knows he is guilty; of course, it will never be proved.
  • Sarah's guest was turned away by the doorman. As a result, she left before the presentations.
  • Sarah's guest was turned away by the doorman; as a result, she left before the presentations.
  • Business is booming. For example, Siemens has made 10 orders since 4 o'clock.
  • Business is booming; for example, Siemens has made 10 orders since 4 o'clock.
  • The paper is stuck in the lift. Consequently, we cannot finish the printing.
  • The paper is stuck in the lift; consequently, we cannot finish the printing.
Remember that you cannot use a comma. For example:
  • She does not loathe chess, on the contrary, she quite likes it.
    • (The term "on the contrary" is a transitional phrase. You cannot merge two sentences into one with a comma. You must either start a new sentence or use a semicolon. This is known as a run-on error.)
Here are two more wrong examples:
  • My security guards are not trained in fire-fighting, therefore, we called the fire service.
  • It is extremely foggy, nevertheless, the game will be played.

Start a New Sentence Nine Times out of Ten

Transitional phrases (or conjunctive adverbs) are common. Most of the time, a transitional phrase will start a new sentence. However, you can use a semicolon if you wish a smoother transition. You should not do this too often.

Read more about using semicolons.

The Main Culprit is "However"

The run-on error is most commonly seen with the word "however."
  • I am leaving now, however, I will be back on Wednesday to collect my wages.

Before Careful with "So"

When "so" mean "therefore," it is a transitional phrase and should be followed by a comma. Like all transitional phrases, it should be preceded with a period or a semicolon. For example:
  • We are not in a position to fund the changes. So, the current system will remain until at least April when it will be reviewed again.
Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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See Also

Commas after a transitional phrase Extend a sentence Using semicolons before conjunctions (and, or, but, etc.) Using semicolons in lists Using semicolons to extend a sentence