In general, add commas to set off words and expressions that interrupt the sentence flow (however, on the other hand, by the way, etc.)

In general, add commas to set off words and expressions that interrupt the sentence flow (however, on the other hand, by the way, etc.)

I must admit, however, that your theory is revolutionary.

You probably underestimated, after all, how long it takes to lose weight.

Similarly, participles that are used to interrupt a clause should be surrounded by commas.

She said, crying, that life is unfair.

1. Place Interrupters Between Commas

Add a comma before and after an interrupting word in the middle of a sentence.

I've been following your performance, and I must say, by the way, that you have done an excellent job.

I've been following your performance, and I must say by the way that you have done an excellent job.

It is important to add both comas, that is; never omit one comma and leave the other. Some writers forget to add the closing comma (also known as the appositive comma).

I must say, on the other hand, that the new project requires the support of a strong team.

I must say, on the other hand that the new project requires the support of a strong team.

Interrupting words and expressions must be placed between commas because they add nonessential information, which does not define or limit.

I underestimated, after all, how expensive it is to move out of your parents' house.

Note that the interrupter ("after all" in the example above) can be safely omitted without changing the meaning of the sentence.

Instead of interrupting a sentence, these expressions may introduce a new sentence. In this case, the transition word should be preceded by a semicolon or a period, not a comma.

I would like to invest in copper; however, this type of investment is particularly risky for small traders.

2. When Not to Use Commas

Do not use commas when a transition word (first, last, next, etc.) is functioning as an adjective or an adverb.

I next add the eggs one at a time, beating after each addition.

As you can expect, the last step is developing a contingency plan.

There are situations where you can decide whether to put commas around the transition word; for example, if the interruption is slight, you can omit them.

Beat the mix until combined, and finally add sugar and vanilla extract.

In contrast, if you want to emphasize the word as an interrupter, set it off with commas.

Beat the cream cheese, and, finally, add sugar and vanilla extract.

But do not use commas if the word is necessary to understand the complete meaning of the sentence.

Beat the mix until fully combined.

3. Participles as Interrupting Words

A participle is a word formed from a verb (e.g., been, being, played, doing.) and used as an adjective or a noun. Participles can also serve as an interrupting word in the middle of a sentence.

After practicing yoga, my wife, relaxed, took a bubble bath.

Generally, participles that come after the noun they describe should be surrounded by commas.

I gently kissed Olivia down along the slope of her nose, ending at her lips; then, she, smiling, stroked the back of my neck.

Note that a participle in mid-sentence is not always an interrupting word. Note the difference between "ending" and "smiling" in the example above.

Another example:

After walking such a long distance, the explorer, confused and exhausted, didn't know where to go or what to do.

4. Common Interrupting Words

Some of the most commonly used interrupting words and expressions are:

• after all
• by the way
• however and nevertheless
• on the other hand
• namely, specifically, or "that is"
• too
• "in contrast" and "by contrast"
• on the contrary
• other interrupting words such as yes, no, etc.

4.1 After all

Typically, we place "after all" between commas in the middle of a sentence when meaning "despite problems or doubts".

She has been, after all, my best friend for eight years.

4.2 By the way

The expression "by the way" must be placed between commas or other proper punctuation marks, such as semicolon or em dashes.

I need to start exercising and, by the way, stick to it.

We do not frequently use commas around "by the way" to indicate a way or method of doing something.

I realized that he is a great actor by the way he talks.

But use commas to set apart nonessential phrases and expressions containing "by the way".

I realized, by the way he talks, that he is a great actor.

4.3 However and Nevertheless

Frequently, we put commas around "however" and "nevertheless" to signal a pause in the middle of a sentence.

Karen enjoys playing basketball. Her favorite sport, however, is soccer.

"Nevertheless" is slightly more formal than "however".

Peter is extremely intelligent, nevertheless, too young to lead the project.

4.4 On the other hand

"On the other hand" should be surrounded by commas in the middle of a sentence to introduce a new perspective or contradict a previous remark.

Nancy likes playing video games. Her sister, on the other hand, prefers to watch horror movies.

4.5 Namely, Specifically and 'That is'

We use commas to set apart "namely", "specifically", or "that is" in mid-sentence before providing further details about something we have just said.

I'd like to visit Southeast Asia, namely, Vietnam, Thailand, and Myanmar.

4.6 Too

We usually put commas around the word "too" in mid-sentence.

Alice, too, thinks that inflation is caused by increases in production costs.

We do not commonly insert a comma before "too" at the end of a sentence.

I love you too.

4.7 'In contrast' and 'By contrast'

Use commas before and after "by contrast" or "in contrast" to signal a pause in the middle of a sentence.

Mary is funny and friendly. Her sister, by contrast, is distant and cold.

Similarly, use commas to separate an interrupting phrase starting with "in contrast" to describe a sharp difference between two ideas, situations, or perspectives.

Thai cuisine, in contrast to conventional European food, uses a wide variety of exotic herbs and spices.

4.8 On the contrary

Use commas to set off "on the contrary" in mid-sentence to express that the previous statement is incorrect or that, actually, the opposite is true.

I think that the new employee is hard-working and proactive. My partner, on the contrary, thinks that she is unprofessional and passive.

4.9 Other interrupters

Occasionally, words such as "yes" and "no" should be surrounded by commas to interrupt the sentence flow.

Make a decision, yes or no, before Friday.

Appearing at the start of a sentence, introductory words like "well", "why", or "hello" are typically followed by a comma. We do not usually use these words, however, in the middle of a sentence.

Well, Barbara didn't go to the party because she had to prepare for an exam.