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 of ruler

• monarch
• emperor
• sovereign
• 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

Last spring, a company owned by the rulers of the United Arab Emirates bought two billion dollars’ worth of USD1. —David D. Kirkpatrick, New Yorker, 31 Jan. 2026

At the same time, Neptune, your celestial ruler, enters Aries, shifting your focus from self-discovery to self-worth. —Valerie Mesa, PEOPLE, 30 Jan. 2026

Niger’s military ruler accused France, Benin, and Côte d’Ivoire of sponsoring an attack on the country’s international airport — without providing any evidence. —Preeti Jha, semafor.com, 30 Jan. 2026

Because this eclipse squares Uranus, your modern ruler, changes may feel sudden or destabilizing at first. —Dossé-Via Trenou, Refinery29, 29 Jan. 2026

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