subject

[joon]

(example) A number in standard form is separated into groups of three digits USING commas.


In the example, What is the subject of the word USING?

In order to make an answer for that, I made the next question.

Who use commans?
We use commas.

So, I think that the general people "we" is the subject of the word USING.

And the phrase "using commas" is a participial construction in grammatical term.


Do you agree with me?

[Celeste]

A number in standard form is separated into groups of three digits USING commas.

In this example, using is a gerund. You could rewrite the sentence with the preposition "by" before the word using.

The whole sentence is written in the passive, suggesting that the subject of the sentence is unimportant or unknown(ie. one).

You could rewrite it in the active voice like this:

One separates a number in standard form into groups of three digits by using commas.

[joon]

This might be the first time I've ever seen the omission of a preposition.

I didn't know preposition can be omitted.

Thank you very much.

By the way,

I can't deduce why the preposition "by" was ommitted in the original sentence.

Are there any generalized principles in omitting a preposition?

[Celeste]

There are some instances where you could choose to use a preposition or not. Sometimes when you have an indirect object, it is common to leave out prepositions, but this changes the word order as well.

Example: He gave the apple to me.

He gave me the apple.


In the case we were talking about before, when discussing HOW something is done, it is okay to leave out the preposition "by" if you are using a gerund.

[joon]

Yes, an indirect object can stand alone without a preposition.
It's one of commonly used structure patterns in English.

Going back to the first case,
would you give me a couple of example sentences leaved out the preposition "by" with the gerund-form headword?