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

See Examples For:

sister sisters

So if you complimented somebody’s jacket, a more acceptable response might be, “Thanks! My sister helped me pick it out.”

From The Wall Street Journal ● Oct. 12, 2026

My sister is a nurse who works three days a week.

From MarketWatch ● Oct. 12, 2026

Your sister is taking care of your mom out of love, but she is understandably aware of the monetary advantages.

From MarketWatch ● Oct. 12, 2026

I don’t think my sister is stealing, and I don’t think she’s being outrageous.

From MarketWatch ● Oct. 12, 2026

We suddenly found a regular thing about her — her sister.

From "Firegirl" by Tony Abbott

Demi Pearson, 15, her brother Brandon, eight, and sisters Lacie, seven, Lia, three, died at their Walkden home in December 2017.

From BBC ● Oct. 12, 2026

Both women, and another of Mr Boyle's sisters, Leanne Boyle, described the impact his death has had on the "very close" family, describing him as "popular" and "kind".

From BBC ● Oct. 9, 2026

“Miss America” is about another one of your sisters.

From Los Angeles Times ● Oct. 9, 2026

Although he grew up in a close family in San Mateo, Calif., his three older sisters loved teasing “Little Tommy” that he was the worst athlete in the family.

From The Wall Street Journal ● Oct. 9, 2026

But there was no need for worry; the famous Fox sisters were given special treatment.

From "American Spirits" by Barb Rosenstock

Related Words

• relative
• twin