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

The diamond, which is over 105 carats, had been passed around by various rulers throughout its early life, and eventually was brought back to India in 1813 and into the hands of ruler Ranjit Singh. —Amethyst Martinez, USA Today, 30 Apr. 2026

The ensuing rulers, the Joseon monarchy, did their predecessors one better. —Lori Waxman, Chicago Tribune, 29 Apr. 2026

Skipping that meeting and quitting OPEC at the same time will be seen as a snub to Saudi’s de facto ruler, Crown Prince Mohammed bin Salman. —Matthew Martin, semafor.com, 28 Apr. 2026

Still, Venus — the moon’s ruler — will meet with powerhouse Pluto today, which is where things could get interesting. —Valerie Mesa, PEOPLE, 28 Apr. 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