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

Just three years’ earlier, an Iron Age tribe living in present-day southeast England known as the Atrebates ousted their ruler named Verica, who subsequently fled for Rome. — Andrew Paul, Popular Science, 5 Nov. 2026

Popping students on the hand or arm with a ruler counts as assault, even if it’s done by a teacher, according to investigators in North Carolina. — Mark Price november 3, Charlotte Observer, 3 Nov. 2026

The film follows a group of young assassins trained by Master, the absolute ruler of a tropical rainforest. — Liz Shackleton, Deadline, 3 Nov. 2026

Tuesday’s elections in the United States – the world’s second-largest democracy – will again serve as a way for citizens to decide which party will be the legitimate ruler. — The Monitor's Editorial Board, Christian Science Monitor, 3 Nov. 2026

Word History

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing ruler

• co-ruler

Rhymes for ruler

• cooler
• 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