Using a Comma after However (i.e., a Transitional Phrase)

The Quick Answer
When a term like However, As a result, or Consequently starts a sentence, it should be followed by a comma. (These terms are called transitional phrases or conjunctive adverbs.)

A transitional phrase sits at the start of a sentence and acts like a bridge to an idea in the previous sentence. Common ones are However, Consequently, Therefore, and As a result.

A transitional phrase is followed by a comma. A transitional phrase is never preceded by a comma.

Using a Comma after a Transitional Phrase (e.g., However )

It is common for a sentence to start with an introduction that acts like a bridge to the previous sentence. The introduction makes the transition between the two sentences smoother. (It is known as a transitional phrase or a conjunctive adverb.)

A transitional phrase always appears at the start of a sentence and is followed by a comma. For example:
  • Bruce Leonard spent 4 years in Japan studying Kung Fu. As a result, he is often able to predict moves by Japanese opponents.
    • (As a result is a transitional phrase. It acts like a bridge between the previous sentence and the new one. It is followed by a comma.)
  • Mark was separated from his twin sister when they were both one. Of course, it was often said that the girl next door looked a little like him, but no one had any reason to think they might be related.
    • (Of course is a transitional phrase.)
  • In summary, 70% of you will fail the course.
  • Consequently, I cannot tolerate sloppy work.
  • Consequently, his teaching techniques are flawed.
  • However, Bruce was unaware that the shark was only making its first pass.

Beware Using a Comma before However

The word However is a very common transitional phrase. It is just like the other transitional phrases, but it deserves a special mention because writers often mistakenly precede it with a comma (as opposed to using it to start a sentence).

Examples:
  • I don't like cake. However, I love scones.
  • I don't like cake, however, I love scones.
When However is being used as a transitional phrase, preceding it with a comma is a mistake called a run-on sentence.

On occasion, it might be appropriate to precede however with a semicolon. For example:
  • I don't like cake; however, I love scones.
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See Also

Using commas (a summary) Our big commas test Run-on errors with commas Using semicolons before transitional phrases (e.g. however) Using semicolons to extend a sentence Commas after a sentence introductions Commas after interjections (yes, no, indeed) Commas before conjunctions (and, or, but) Commas for parenthesis Commas in lists Commas with a long subject Commas with numbers Commas with quotation (speech) marks Commas with the vocative case Commas with Dear, Hello, and Hi