sis‧ter S1 W1 /ˈsɪstə $ -ər/ noun [countable]
[Language: Old English; Origin: sweostor]

1. a girl or woman who has the same parents as you ⇒ brother, half-sister, step-sister:
Janet and Abby are sisters.
He has two sisters and a brother.
older/big sister
My older sister is a nurse.
younger/little sister
Where’s your little sister?
She’s my twin sister.

2. sister paper/publication/company etc a newspaper etc that belongs to the same group or organization:
the Daily Post’s sister paper, the Liverpool Echo

3. (also Sister) a nun:
Good morning, Sister Mary.

4. British English (also Sister) a nurse in charge of a hospital ward:
the ward sister
I’m feeling a bit better today, Sister.

5. a word used by women to talk about other women and to show that they have feelings of friendship and support towards them:
We appeal to our sisters all over the world to stand by us.

6. American English spoken a way of talking to or about an African-American woman, used especially by African Americans

[TahlilGaran] Dictionary of Contemporary English ▲

sister
noun
ADJ. big, elder, older | baby, kid, little, small, wee, younger | twin | full (= sharing both parents) | half-(= sharing one parent), step-(also stepsister) (= the daughter from an earlier marriage of your stepfather or stepmother) | beloved, much-loved | dead, deceased, late | unmarried
PHRASES brother and sister Have you got any brothers and sisters?
like sisters The girls are so close, they're like sisters.

[TahlilGaran] Collocations Dictionary ▲

sister

an older sister (also an elder sister especially British English)
He had two older sisters, Karen and Jacqueline.
a big sister (=an older sister)
She misses her big sister dreadfully.
a younger sister
Mary showed a lot of aggressive behaviour towards her younger sister.
a little/kid sister (=a younger sister)
She was very fond of her little sister.
a baby sister (=a sister who is still a baby)
He wanted a baby sister.
a twin sister
He is devoted to his twin sister.
a half-sister (=a sister with only one parent the same as yours)
She doesn't see her half-sister very often.

[TahlilGaran] Collocations Dictionary ▲