A proportion of a group or an amount is a part of it.

The proportion of one kind of person or thing in a group is the number of people or things of that kind compared to the total number of people or things in the group.

The proportion of one amount to another is the relationship between the two amounts in terms of how much there is of each thing.

If you refer to the proportions of something, you are referring to its size, usually when this is extremely large.

If you refer to the proportions in a work of art or design, you are referring to the relative sizes of its different parts.

If one thing increases or decreases in proportion to another thing, it increases or decreases to the same degree as that thing.

If something is small or large in proportion to something else, it is small or large when compared with that thing.

If you say that something is out of all proportion to something else, you think that it is far greater or more serious than it should be.

If you get something out of proportion, you think it is more important or worrying than it really is. If you keep something in proportion, you have a realistic view of how important it is.

If someone has a sense of proportion, they know what is really important and what is not.