means shortening it to a phrase.

So to reduce an adverb clause of time,

we need a time word and a present participle.

That's the -ing form of the verb.

Look at this example.

The present participle has an active meaning,

so it's understood that the subject is doing the action.

We can only form a phrase from an adverb clause

if the subjects of the two clauses are the same.

Who fell asleep? I did.

Who began to have strange dreams? I did.

So the subjects are the same.

That's why we can use this phrase.

Look at this new sentence.

Can the adverb clause be reduced to a phrase?

No. The subjects are different.

Here's how you make an adverb clause a phrase.

And remember with that present participle

you're expressing an active meaning.

We don't always use a time word

when we shorten an adverb clause of time.

While is often omitted because it's understood.

Hopefully, you understand how I wrote this sentence in the story.

Let me point out that the full adverb clause

could be written a different way.

After "while" there could be a progressive verb:

"While two children were sleeping..."

That makes sense, too.

Again, the process would be the same.

We remove any helping verb.

- in this case a form of BE.

And our main verb is already a present participle.

So this makes our job easier.

When we change adverb clauses with progressive verbs,

just take out the form of BE

and keep the present participle.

I mentioned that we often omit "while"

when we create these phrases.

We sometimes omit "when," too.

I did this in the story.

Look at this example.

When is understood, so I left it out.

My story isn't very formal,

but in more formal English I could have written:

"Upon" is a time word that has the meaning of "when."

Let's talk for a moment about word order.

These phrases that act like adverbs

are usually in an initial position.

At the beginning of a sentence.

But they can also be in a final position.

Let's look at some examples.

Here are two lines from the story.

In both sentences, the phrase comes before the main clause.

Commas are generally used for separation.

Now compare those examples to these.

I have two more lines from the story.

In these two sentences, the phrase comes after the main clause.

Commas aren't always used for separation in this case.

In the first sentence, I chose not to use a comma.

The phrase is quite short.

In the second, we have a longer phrase.

Most writers would use a comma here.

It helps the reader to separate the two ideas.

I'd like you to try a very short exercise to test your understanding.

I'll give you three sentences.