ruler
Americannoun
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a person who rules or governs; sovereign.
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Also a strip of wood, metal, or other material having a straight edge and usually marked off in inches or centimeters, used for drawing lines, measuring, etc.
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a person or thing that rules paper, wood, etc.
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Astrology. the planet primarily associated with any sign of the zodiac or any house of the horoscope.
The ruler of Aries is Mars. The ruler of Taurus is Venus.
noun
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a person who rules or commands
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Also called: rule. a strip of wood, metal, or other material, having straight edges graduated usually in millimetres or inches, used for measuring and drawing straight lines
Other Word Forms
Derived Forms
Etymology
Origin of ruler
Middle English word dating back to 1325–75; see origin at rule, -er 1
Explanation
The leader of a country is a ruler. If you're a queen, a sultan, or a czar, you're a ruler. Besides "person who rules or governs," you can define ruler as a measuring device that's marked with inches or centimeters. You can measure the diameter of a circle with a ruler, and you can also draw a perfectly straight line using its edge. Both meanings stem from the verb rule, "to exercise power" or "to control," which came to also mean "mark with lines" in the 1590s.
Vocabulary lists containing ruler
Measurement and Data, List 2
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"Culture Clash"
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Measurement and Data
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The role of Qatar in talks has grown and its state news agency said late Thursday that Trump had called its ruler to discuss the "latest updates" on efforts to end the war.
From Barron's • May 29, 2026
Some believe that when MBS became de facto ruler of the Kingdom in 2017, he inherited a system that badly needed overhauling.
From BBC • May 25, 2026
Libya has remained fractured since chaos broke loose following the 2011 Arab Spring uprising that toppled longtime ruler Muammar Gaddafi.
From Barron's • May 17, 2026
Made of 15-karat gold, this helmet is believed to have been worn by an early Sumerian ruler.
From The Wall Street Journal • Apr. 16, 2026
Whipping out the packet he selected a nut and popped it straight into the open beak of the astonished ruler.
From "Redwall" by Brian Jacques
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
