1. A part or amount considered in relation to a whole: What is the proportion of helium in the atmosphere?
2. A relationship between things or parts of things with respect to comparative magnitude, quantity, or degree: the proper proportion between oil and vinegar in the dressing.
3. A relationship between quantities such that if one varies then another varies in a manner dependent on the first: "We do not always find visible happiness in proportion to visible virtue" (Samuel Johnson).
4. The agreeable or harmonious relation of parts within a whole: The statue seems out of proportion.
5. often proportions Dimensions; size: First measure the proportions of the room.
6. Mathematics A statement of equality between two ratios. Four quantities, a, b, c, d, are said to be in proportion if a/b = c/d .
tr.v. pro·por·tioned, pro·por·tion·ing, pro·por·tions
1. To adjust so that proper relations between parts are attained: Have you proportioned the oil in the dressing properly?
2. To form the parts of with balance or symmetry: The artist proportioned the figure nicely.
[Middle English proporcion, from Old French proportion, from Latin prōportiō, prōportiōn-, from prō portiōne, according to (each) part : prō, according to; see PRO-1 + portiōne, ablative of portiō, part; see perə-2 in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.