- For the math equations, see: Proportions.
A proportion (adjective: proportionate) is a relationship between two quantities or numbers. A proportion can be expressed as a word, for example, one man may be described as smaller than another man. A proportion can usually be expressed more precisely by numbers. For example, the proportion, or mathematical relationship, between one man and two men can be written as the numbers "1/2", which is also known as a fraction or ratio.