Using a Comma after an Adverbial Clause or Phrase
at the Start of Sentence

The Quick Answer
When words which "set the scene" for the main part of the sentence appear at the front of the sentence, it is usual to offset them with a comma. For example:
  • At 4 o'clock, I'll jump in the river.
  • As I know the ground, I'll go first.
  • Under the water, you can see the swans' legs going hell for leather.
(NB: These "scene setting" words of introduction are called adverbial clauses or adverbial phrases.)

When the introduction is just one word (e.g., Yesterday, Here, Now), it is common to omit the comma.

Using a Comma after an Introductory Adverbial Clause or Phrase

It is common for a sentence to start with an introduction. An introduction can be anything from just one word to a long clause.

An introduction is used to state a time, a place, a condition, a frequency, or a fact before the main part of the sentence.

These "introductions" vary hugely. They are known as dependent clauses because they cannot stand alone as complete ideas. If an "introduction" contains its own subject and verb, it will be an adverbial clause, otherwise it will be an adverbial phrase. The main part of the sentence (i.e., the clause after the "introduction") is called an independent clause.

Read more about clauses and phrases.

Examples of Introductory Adverbial Clauses and Adverbial Phrases

In these examples, the introductory adverbial clauses and adverbial phrases are shaded:
  • In the centre of London, the number of people who fell victim to pickpockets rose by 30 per cent in a month.
  • (This adverbial phrase sets a place.)

  • After twelve years of therapy, my psychiatrist said something that brought tears to my eyes. He said, "No hablo ingles."
  • (This adverbial phrase sets a time.)

  • In ancient Rome, it was considered a sign of leadership to be born with a crooked nose.
  • (This adverbial phrase sets a place and a time.)

  • As soon as the cake is golden-brown, take it out of the oven.
  • (This adverbial clause sets a time.)

  • From the moment I picked your book up until I laid it down, I was convulsed with laughter. Someday, I intend reading it. (Groucho Marx)
  • (The first is an adverbial phrase that sets a time. The second is an adverbial phrase that sets a time.)

  • When I was young, I used to think that money was the most important thing in life. Now that I am old, I know it is. (Oscar Wilde)
  • (Both adverbial clauses set a time.)

  • On Tuesday 4th July a band played carols in the park for 8 hours.
  • (The adverbial phrase On Tuesday 4th July sets a time. It is an introduction and should be followed by a comma.)

  • Having spoken to John, I can confirm that the meeting is definitely off.
  • (The phrase Having spoken to John states a fact that "sets the scene." This type of phrase is known as a participle phrase.)

  • As you are well aware, the latest figures do not look promising.
  • (The adverbial clause As you are well aware states a fact that "sets the scene.")

  • After the secretary had read the minutes of the meeting, the chairman asked for the financial report.
  • (The adverbial clause After the secretary had read the minutes of the meeting sets a time.)

  • A band played in the park for 8 hours on Tuesday 4th July.
  • (The adverbial phrase on Tuesday 4th July sets a time, but it is not an introduction. It is at the back end of the sentence. Therefore, no comma is required.)

  • On Tuesday 4th July, a band played in the park for 8 hours.
  • (Compare this example to the one above.)

  • If you are going through hell, keep going. (Winston Churchill)
  • (This adverbial clause sets a condition.)

Different Types of Adverbs

Adverbs (either clauses or phrases) at the start of a sentence vary hugely. Here are some examples of the different types:

Adverbs of Time

  • When the cake is brown, remove it from the oven.

Adverbs of Place

  • In the middle of the park, there will be band.

Adverbs of Manner

  • Crawling on hands and knees, he move along the ledge.

Adverbs of Degree

  • More stealthily than ever before, he tiptoed past his parents' room.

Adverbs of Condition

  • If it snows, the lights will look amazing.

Adverbs of Concession

  • Even though she has no teeth, he is still handsome.

Adverbs of Reason

  • Since you asked nicely, you can have my last sweet.
Read more about the different types of adverbs.

See Also

Using commas (a summary) Try our commas test Commas after a transitional phrase 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