Meaning of “proportion” - Learner’s Dictionary

proportion

noun uk us /prəˈpɔːʃən/

[ C ] a part of a total number or amount:

Children make up a large proportion of the world's population.
The class consists of both men and women in roughly equal proportions.
out of proportion

If something is out of proportion, it is much bigger or smaller than it should be, when compared to other things:

The punishment is completely out of proportion to the crime.
in proportion

If something is in proportion, it is the right size or shape when compared to other things.

in proportion to

If something changes in proportion to another thing, it changes to the same degree as that thing:

Your tax payment increases in proportion to your salary.

(Definition of “proportion” from the Cambridge Learner’s Dictionary © Cambridge University Press)