sister

noun

sis·​ter ˈsi-stər 

1

: a female who has one or both parents in common with another

2

often capitalized

a

: a member of a women's religious order (as of nuns or deaconesses)

especially : one of a Roman Catholic congregation under simple vows

b

: a girl or woman who is a member of a Christian church

3

a

: a girl or woman regarded as a comrade

b

: a girl or woman who shares with another a common national or racial origin

especially : a Black girl or woman

4

: one that is closely similar to or associated with another

sister cities

5

chiefly British : nurse

6

a

: girl, woman

b

: person

—usually used in the phrase weak sister

7

: a member of a sorority

Examples of sister in a Sentence

The sisters live in the convent.

Recent Examples on the Web

The summer program officials said that Camp Mystic Cypress Lake, a sister site that opened in 2020, will be open in summer 2026, while Camp Mystic Guadalupe River will not be able to reopen by then due to the devastating damage sustained earlier this year. —Jon Haworth, ABC News, 24 Sep. 2025

Though no longer competing, Arnold’s younger sister Rylee is a Season 34 pro, partnered with Pentatonix singer Scott Hoying. —Amanda Castro, MSNBC Newsweek, 24 Sep. 2025

Kirkpatrick said none of them had ever had Sweetgreen before, but her sister lives in California and had been raving to the family about it. —Endia Fontanez, AZCentral.com, 23 Sep. 2025

The show also starred Katey Sagal as matriarch Cate Hennessy, Amy Davidson as Bridget's sister Kerry and Martin Spanjers as her brother Rory. —Charna Flam, PEOPLE, 23 Sep. 2025

Word History

Etymology

Middle English suster, sister, partly from Old English sweostor and partly from Old Norse systir sister; akin to Latin soror sister, Sanskrit svasṛ

First Known Use

before the 12th century, in the meaning defined at sense 1

Phrases Containing sister

• big sister
• brother/sister/comrade in arms
• foster brother/sister
• half sister
• little brother/sister
• sister chromatid
• sister city
• sister-in-law
• sob sister
• soul sister
• weak sister

Rhymes for sister

• blister
• lyster
• mister
• twister
• resister
• resistor
• stepsister
• transistor

Kids Definition

sister

noun

sis·​ter ˈsis-tər 

1

: a female who has one or both parents in common with another individual

2

often capitalized : a member of a religious community of women : nun

3

a

: a fellow female member of a group

b

: a girl or woman who shares a common national or racial origin with another

4

: one that is closely similar to or associated with another

sister schools

sister ships

5

chiefly British : nurse entry 1 sense 2

sisterly adjective or adverb

Medical Definition

sister

noun

sis·​ter ˈsis-tər 

chiefly British

: a head nurse in a hospital ward or clinic

broadly : nurse