پایگاه آموزش زبان انگليسي معصوم پور

2. Expressing the idea of
“During the same time” in modifying phrases:
Examples:
While he was reading, he felt very upset.
While reading, he felt very upset.
Reading, he felt very upset.
Going home, she saw an ancient car on the sidewalk.

Sometimes while is omitted but the -ing phrase at the beginning of the 
sentence gives the same meaning (= during the same time)

3. Expressing 
cause and effect relationships in modifying phrases:

Because is not used in a modifying phrase. It is omitted, but
the resulting phrase expresses a cause and effect relationship.

Because he worked, he didn’t come to attend the speech.
Working, he didn’t come to attend the speech.

Often an -ing phrase at the beginning of a sentence gives the 
meaning of “because”.

Because she has moved, she doesn’t remember the way to the market.
Having moved, she doesn’t remember the way to the market.

Having + past participle gives the meaning not only of because, but 
also of before.

Because he was unable to afford the truth, he lied a lot. 
Being unable to afford the truth, he lied a lot.
Unable to afford the truth, he lied a lot.

 The form of be in the adverb clause is often changed to being. The 
use of being makes the cause and effect relationship clear.