Commas after a transitional phrase
 
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.
 

Comma after a Transitional Phrase

It is common for a sentence to start with an introduction that acts like a bridge between the last sentence and the new sentence. The introduction makes the transition between the two sentences smoother. (It is known as a transitional phrase.) It always appears at the start of a sentence and is followed by a comma.

Examples:

Bruce Leonard spent 4 years in Japan studying Kung Fu and 3 years at the
London School of Martial Arts as the senior instructor. As a result, his style...
(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.)

Of course, he never knew…  
(Of course, < transitional phrase)

In summary, 7 out of 10…  
(In summary, < transitional phrase)

Therefore, the cost of each lesson…  
(Therefore, < transitional phrase)

Consequently, his teaching techniques…  
(Consequently, < transitional phrase)

However, Bruce was unaware…  
(However, < transitional phrase)
 
YOU CAN USE SEMICOLONS 

On occasion, you may wish to use a semicolon before a transitional phrase to make the transition between sentences even more seamless. (This is covered in lesson Semicolons.)

I cannot come on Tuesday. However, Peter will be there.
(However, - transitional phrase)
I cannot come on Tuesday; however, Peter will be there.
(however, – transitional phrase using a semicolon)

DON'T OVERUSE SEMICOLONS 

Transitional phrases are useful because they keep ideas flowing between sentences. Most of them should be preceded by full stops ( periods). If you use semicolons before all your transitional phrases, you'll annoy your readers. Semicolons are great in moderation. Hold them back for when you want a really smooth transition between two sentences.
 
 
NOT A COMMA 

You cannot use a comma before a transitional phrase.

I cannot come on Tuesday, however, Peter will be there.

This is a very common error – especially with however.

See also: Run-on errors with commas
 

See also:

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
List of easily confused words


>