In previous units you learned to use gerunds after prepositions:

She is good at playing the piano. They went to dinner after performing at the National Theater.

We can also gerunds after prepositions with specific expressions to apologize or express regret about finished situations or events in the recent past. As you know, recent finished events in the past are usually expressed with the PRESENT PERFECT. Lets examine a past situation that we regret or want to apologize for:

You have invited a friend to concert. The concert has turned out to be terrible. If you want to apologize for the invitation you start saying something like this:

I’m sorry for…. I want to apologize for…..

As you know, for is a preposition. You also know that prepositions are always followed by gerunds when the word after them is a verb.

So the next word after for in our example should be: