1. in proportion: having the correct relationship of size, quantity, or degree to something else, or remaining in the same relationship when things change The rate of pay is proportional to the complexity of the task.
2. mathematics related by ratio: related by or possessing a constant ratio
noun (pluralpro·por·tion·als)
Definition:
mathematics term in pair of equivalent ratios: one of the four terms in a relationship of proportion between two ratios, where the first term divided by the second equals the third divided by the fourth
[14th century. < late Latin proportionalis< Latin proportion- (see proportion)]