An adverbial clause is a subordinate clause‏‎ that act as the adverb in a sentence. It normally answers the questions: how, when, where, how much.

We can join two clauses using a simple conjunction.

She heard the door open while she was watching television.

The second clause can be turned into an adverbial clause by using the present participle.

She heard the door open while watching television.

We can use the present participle by itself to show something happening simultaneously or just previously to the main event.

Watching TV, she heard the door open.

Laughing, I walked out.

Standing up, he introduced himself.

N.B. Using perfect forms makes the construction more formal.

Standing up, he introduced himself.

(spoken; informal)

Having stood up, he introduced himself.

(written; formal)

These types of sentences are all examples of reduction. See below for more on this.

Reduction of Adverbial Clauses

An adverbial clause can be reduced to a word when the main clause and the adverbial (subordinate) clause have the same subject.

My sister snores while she sleeps.

My sister is the subject of both the main clause My sister snores and the subordinate clause while she sleeps.

How to Reduce

There are two ways in which you can reduce an adverbial clause to a phrase. You use one or the other according to whether the adverbial clause is in the past continuous (or progressive) or in the simple past (past tense).

• Adverbial clause in the past continuous (or progressive)

While she was chopping the onions, she cut her finger.

To reduce this adverbial clause simply drop the subject and the verb to be.

While chopping the onions, she cut her finger.

• Adverbial clause in the simple past

Before we sat down for dinner, we always washed our hands.

To reduce this adverbial clause simply drop the subject and turn the past tense into a gerund.

Before sitting down for dinner, we always washed our hands.