ruler

noun

rul·​er ˈrü-lər 

1

: one that rules

specifically : sovereign

2

: a worker or a machine that rules paper

3

: a smooth-edged strip (as of wood or metal) that is usually marked off in units (such as inches) and is used as a straightedge or for measuring

rulership

ˈrü-lər-ˌship 

noun

Synonyms

• monarch
• sovereign
• emperor
• king

Examples of ruler in a Sentence

a summit attended by a number of rulers from around the world

This ruler shows inches and centimeters.

Recent Examples on the Web

The ultimate ruler on the appeal of the board’s decision is the board. —Mercury News Editorial, Mercury News, 27 June 2025

But today’s escalating tensions go back to 1953, when British oil companies and the CIA orchestrated a coup and installed the Shah of Iran, a secular ruler willing to accommodate Big Oil and other corporate interests in the West. —Robert Polner, New York Daily News, 23 June 2025

Art and creativity flourished under her rule, with the Deir el-Bahri complex built during her time as ruler. —Rachael O'Connor, MSNBC Newsweek, 23 June 2025

Germany's Chancellor Friedrich Merz also discussed the Israel-Iran conflict with Qatar's ruler ahead of the Geneva talks. —Arkansas Online, 20 June 2025

Word History

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing ruler

• co-ruler

Rhymes for ruler

• cooler
• jeweller
• schooler
• schuller
• preschooler
• vestibular

Kids Definition

ruler

noun

rul·​er ˈrü-lər 

1

: sovereign entry 1 sense 1

2

: a straight strip of material (as wood or metal) marked off in units and used as a guide in drawing lines or for measuring