Can we say "John is the stiffest of Rachel and Mark.", OR "John is more stiffer than Rachel and Mark."?
Which one is better?
Both are wrong. A person can only be 'the [adjective]est' of a group which includes them, so if Rachel and Mark are John's brother and sister you could say 'John is the stiffest one of the family'. Otherwise it has to be 'John is stiffer than Rachel and/or Mark'.
answered Nov 13 '18 at 19:50
-
+1 Exactly. I would use than either Rachel or Mark or than both Rachel and Mark. – Jason Bassford Nov 13 '18 at 19:52
When we compare more than two things we must use the superlative degree form. In your case, it is 'the stiffest'. The other /comparative degree form 'stiffer' / is grammatically wrong. The double comparison /'more stiffer'/ is impossible.
-
You can't say X is the stiffest of Y and Z. X doesn't belong to the group consisting of Y and Z. You can only say "X is the stiffest of X, Y, and Z." – Jason Bassford Nov 13 '18 at 19:49
more stifferis not accepted form, refrain from using it. – Ayxan Nov 13 '18 at 12:55