which is right?

[vladz]

Hi! I am wondering if the sentence "MArk is less taller than Paul" is correct. Please advise me. Thanks.

[Casiopea]

Hi! I am wondering if the sentence "MArk is less taller than Paul" is correct. Please advise me. Thanks.

The opposite of 'tall' is 'short':

Mark is less taller than Paul. :( (ungrammatical)
Mark is shorter than Paul. :D (grammatical)

[henry]

Hi! I am wondering if the sentence "MArk is less taller than Paul" is correct. Please advise me. Thanks.

I agree with Ca. In addition: Mark is not taller than Paul.( same tall) :wink:

[Casiopea]

Hi! I am wondering if the sentence "MArk is less taller than Paul" is correct. Please advise me. Thanks.

I agree with Ca. In addition: Mark is not taller than Paul.( same tall) :wink:

as tall as means, around the same height.
not taller than means, Mark could be around the same height as Paul or he could be shorter than Paul.

All the best,