At the beginning of a sentence, transition words such as "of course" and "certainly" are often followed by a comma. Some style guides, however, consider that this comma is not always necessary.

At the beginning of a sentence, transition words such as "of course" and "certainly" are often followed by a comma. Some style guides, however, consider that this comma is not always necessary.

Certainly, he is one of the best players of the league.

Of course she isn't.

We do not commonly place commas to set off these expressions in mid-sentence. But you can use them to signal a strong interruption or add nonessential information.

She is certainly one of the best tennis players in the world.

I would say that Hegel was a great philosopher and, of course, a wise man.

1. Commas Before and After 'Of course'

We commonly use "of course" to express that a situation or fact is not surprising.

It's a public holiday. Of course, most retail stores are closed.

At the start of a sentence, we often use "of course" as a conjunctive adverb or an interjection.

Of course, you should attend the meeting.

Conjunctive adverbs are usually followed by a comma to indicate that they modify not just a word but the sentence or clause that follows.

Of course, you will be under proper adult supervision.

But some style guides argue that you can omit the comma after short transition words like "of course" if the meaning of the sentence is clear.

Of course you can use my car.

We can also use "of course" as an interjection; that is, as an abrupt remark, an aside, or an interruption. Interjections should be followed by a comma or an exclamation point.

Of course! I believe you.

Remember to capitalize the first word after an exclamation point.

Of course! Children should be supervised at all times.

Use the same comma rules when introducing a clause (instead of a sentence) with "of course".

My wife is wealthy and, of course, she can afford to fly first class all the time.

Add a comma before and after "of course" in mid-sentence to stress a pause or introduce parenthetic information (which can be safely removed without changing the meaning of a sentence).

A polar climate is, of course, extremely cold (even in summer).

But no comma is necessary if the interruption is slight.

Family is of course the most important thing in my life.

2. Commas After 'Certainly'

You can use "certainly" as a synonym of:

• "of course" (e.g., "Certainly, you may go.")
• "surely" or "definitely" (e.g., "It certainly is cold outside.")

We usually add a comma after "certainly" at the start of a sentence.

Certainly, you may be exposed.

Commas around "certainly" in mid-sentence are often unnecessary.

The organization certainly cannot implement all projects without funding.

She certainly is a talented student.

But you can place a comma before and after a sentence adverb, such as "certainly", to reflect the speaker's judgement, signal a strong interruption, or include an aside.

Inflation is rising and, certainly, a surge in consumer demand may drive consumer prices even higher.