Why the "s" in "le des" here?

Question

Es cortés que le des tu asiento a una persona mayor cuando sube al autobús. Why is there a "s" in "des". Is it because the speaker is directing this to the listener? What purpose does the "s" serve?

Answer 1

You are on the right track.

Is it because the speaker is directing this to the listener?

Yes, because it is being expressed in a form directly to the second person, Tú (rather than the impersonal or 3rd person, as in English saying ¨you are supposed to do this¨ rather than ¨one is supposed to do this¨

It is courteous that you would give your seat to an older person when they get on the bus.

Or as we would more likely say it in English.

It is courteous (for you) to give your seat to and older person... .

Des is the 2nd person informal subjunctive of ¨dar¨, to give.

hth buena suerte