the word "lesson"?

Question

I have confusion on the following:
They have done their lesson/lessons?:
In the dictionary(cambridge) lesson is a countable noun. So it seems that lessons would be right.

But, the following correct sentence is taken from a dictionary(cambridge):
They refuse to work for their living
--- where living is also countable but it means a period of time in which a person is taught about a subject.

thanks for any clarification !

I have confusion on the following:
They have done their lesson/lessons?:
In the dictionary(cambridge) lesson is a countable noun. So it seems that lessons would be right.

But, the following correct sentence is taken from a dictionary(cambridge):
They refuse to work for their living
--- where living is also countable but it means the money that you earn from your job.

thanks for any clarification !

Answer 1

Lesson, being 'countable', can be singular or plural, depending on how many lessons one is taking at a given time.

'Living', in this context, can be taken as singular or plural. I've heard it both ways, but only rarely in the plural. However, 'living' (as a noun) does not mean what you suggest, but rather the material necessities (home, food, clothes, etc.) that make living (as a verb) possible.

Answer 2

both lesson and lessons is correct, due to the structure of the sentence.

Answer 3

i would say lesson, not lessons because you usually cover only one lesson a day... but it's up to you :)