sister

American  

[sis-ter] / ˈsɪs tər /

noun

sisters plural

1. a female offspring having both parents in common with another offspring; female sibling.

2. Also called half sister.  a female offspring having only one parent in common with another offspring.

3. stepsister.

4. a female friend or protector regarded as a sister.

5. a thing regarded as feminine and associated as if by kinship with something else.

   The ships are sisters.

6. a female fellow member, as of a church.

7. a female member of a religious community that observes the simple vows of poverty, chastity, and obedience.

8. British. a nurse in charge of a hospital ward; head nurse.

9. Informal. a term used to refer to or address a fellow Black woman; soul sister.

10. a woman who supports, promotes, or participates in feminism.

11. Informal. a form of address used to a woman or girl, especially jocularly or contemptuously.

    Listen, sister, you've had enough.

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adjective

1. being or considered a sister; related by or as if by sisterhood.

   sister ships.

2. having a close relationship with another because of shared interests, problems, or the like.

   We correspond with school children in our sister city.

3. Biochemistry. being one of an identical pair.

sister British  

/ ˈsɪstə /

noun

1. a female person having the same parents as another person

2. See half-sister stepsister

3. a female person who belongs to the same group, trade union, etc, as another or others

4. informal a form of address to a woman or girl, used esp by Black people in the US

5. a senior nurse

6. RC Church a nun or a title given to a nun

7. a woman fellow member of a Church or religious body

8. (modifier) belonging to the same class, fleet, etc, as another or others

   a sister ship

9. (modifier) biology denoting any of the cells or cell components formed by division of a parent cell or cell component

   sister nuclei

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Other Word Forms

Derived Forms

• nonsister
  noun
• sisterless
  adjective
• sisterlike
  adjective

Inflected Forms

Nouns

• sisters
  plural

Etymology

Origin of sister

First recorded before 900; Middle English (noun) from Old Norse systir; cognate with Old English sweoster, Dutch zuster, German Schwester, Gothic swistar; akin to Serbo-Croatian sèstra, Lithuanian sesuõ, Latin soror (from unattested swesor ), Old Irish siur, Welsh chwaer, Sanskrit svasar “sister,” Greek éor “daughter, niece”

Explanation

Your sister is your female sibling. If your parents have six children, and all of them are girls, that means you have five sisters. Your biological sister has the same mother and father that you have, but some sisters are adopted, or even have a different mom or dad (some people call this a stepsister or a half-sister). If you join a college sorority or a trade union, you'll refer to the other members as your sisters. Catholic nuns and other religious women are also called sisters. The roots of sister go back to words meaning "one's own" and "woman."

Example Sentences

“Father Brown” even spawned a spin-off, “The Sister Boniface Mysteries,” which has been airing on BritBox since 2022.

From Salon • Jun. 16, 2026

Sister Maria nags the girls about dirty rooms and overloaded washing machines, and conducts room checks twice a month.

From The Wall Street Journal • Jun. 11, 2026

"Rubio spoke about aiding the homeless, terminally ill and those afflicted by leprosy," Sister Marie Juan of Missionaries of Charity told reporters after his hour-and-a-half-long visit.

From Barron's • May 23, 2026

Jones recently portrayed Mrs Bennet in another comedy series, The Other Bennet Sister, which was inspired by Jane Austen's Pride and Prejudice.

From BBC • Apr. 10, 2026

She provided her with underpants, something Nhamo found annoying, but Sister Gladys insisted that civilized women wore them.

From "A Girl Named Disaster" by Nancy Farmer

Related Words

• relative
• twin