ratio

noun

ra·​tio ˈrā-shē-ˌō 

-(ˌ)shō

plural ratios

1

a

: the indicated quotient of two mathematical expressions

b

: the relationship in quantity, amount, or size between two or more things : proportion

2

: the expression of the relative values of gold and silver as determined by a country's currency laws

Synonyms of ratio

• rate

Examples of ratio in a Sentence

What is the length-to-width ratio?

the ratio of students to teachers in the school is nine to one

Recent Examples on the Web

Researchers looked at waist circumference and waist-to-hip ratio. — ABC News, 13 Aug. 2026

Hydrogen, which has no neutrons, has roughly double that ratio of any other element, which is why water is often cited as a good space radiation shield. — Jacek Krywko, ArsTechnica, 13 Aug. 2026

The schools were evaluated not just on cost and the quality of schooling, but also on student-faculty ratios and graduation rates using a 100-point scale. — Veronica Fernandez-Alvarado, Sacbee.com, 13 Aug. 2026

Sharp runs the largest such facility in San Diego County and obtained a temporary reprieve on the state’s requirement to begin meeting the 6-to-1 ratio on June 1. — Paul Sisson, San Diego Union-Tribune, 12 Aug. 2026

Word History

Etymology

Latin, computation, reason — more at reason entry 1

First Known Use

1660, in the meaning defined at sense 1a

Phrases Containing ratio

• aspect ratio
• case fatality ratio
• common ratio
• focal ratio
• golden ratio
• gyromagnetic ratio
• loss ratio
• nutritive ratio
• Poisson's ratio
• price-earnings ratio
• ultima ratio

Rhymes for ratio

• acknow
• aglow
• ago
• airglow
• aloe
• altho
• although
• ammo
• backflow
• backhoe
• banjo
• barbeau

Kids Definition

ratio

noun

ra·​tio ˈrā-shō 

-shē-ˌō

plural ratios

1

: the quotient of two numbers or mathematical expressions

the ratio of 6 to 3 may be expressed as 6:3, ⁶⁄₃, and 2

2

: the relationship in quantity, amount, or size between two or more things

women outnumbered men in the ratio of three to one

Medical Definition

ratio

noun

ra·​tio ˈrā-(ˌ)shō, -shē-ˌō 

plural ratios

: the relationship in quantity, amount, or size between two or more things see sex ratio