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

With your celestial ruler, Mars, entering Libra on Aug. 6, everything from your committed relationships to potential prospects takes center stage. —Valerie Mesa, People.com, 7 Aug. 2025

Was their cause a betrayal, or a principled stand against a ruler whose ambitions threatened to consume their way of life? —Jp Mangalindan, Time, 1 Aug. 2025

Public disorder would discredit the local rulers in the eyes of their Papal overlords and possibly lead to dismissal from power. —The Editors, JSTOR Daily, 31 July 2025

The two acts now jointly claim the fifth-most rulers in the history of the list. —Hugh McIntyre, Forbes.com, 30 July 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