Difference between "All" and "All of"?

Question

When I come across a sentence with "All of" or "All", I always get confused between them.

I stopped to greet all my friends.

I stopped to greet all of my friends.

Are there any differences between the sentences above?

Answer 1

I think you meant to say is there a difference between

I stopped to greet all my friends.

and

I stopped to greet all of my friends

These two sentences use different words, but the meaning is identical.

In fact, I suspect that the first is simply a shortened version of the second. That is, if I was transcribing and someone said "all my friends," I would likely write down "all of my friends." It sounds a little more complete, which is what you want in written English. No one will complain if you use the first form, though.

Answer 2

I stopped to greet my friends.

I stopped to greet all of my friends.

Both are grammatical, without any difference in meaning.

When you want to refer to every thing or person in a group, You can use all or all of in front of a possessive determiner + plural noun. However, the use of "all" is far more common than that of "all of".