ra·tio (r??sh?, r??sh?-??)n. pl. ra·tios 1. Relation in degree or number between two similar things.2. The relative value of silver and gold in a currency system that is bimetallic.3. Mathematics A relationship between two quantities, normally expressed as the quotient of one divided by the other; for example, the ratio of 7 to 4 can be written 7:4 or 7/4. A ratio can often also be expressed as a decimal or percentage.[Latin rati?, calculation, from ratus, past participle of r?r?, to reckon, consider; see ar- in Indo-European roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.ratio (?re??????) n, pl -tios1. a measure of the relative size of two classes expressible as a proportion: the ratio of boys to girls is 2 to 1. 2. (Mathematics) maths a quotient of two numbers or quantities. See also proportion6[C17: from Latin: a reckoning, from r?r? to think; see reason]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ra?tio (?re? ?o?, -?i?o?) n., pl. -tios. 1. the relation between two similar magnitudes with respect to the number of times the first contains the second: the ratio of 5 to 2, written 5:2 or 5/2. 2. proportional relation; rate: the ratio between acceptances and rejections. 3. the relative value of gold and silver when both are used as a country’s monetary standard. [1630?40;