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."

Definitions of sister

n a female person who has the same parents as another person

“my sister married a musician”
blood brother, brother
a male with the same parents as someone else
big sister
an older sister
little sister
a younger sister
half sister, half-sister, stepsister
a sister who has only one parent in common with you
Type of:
female sibling
a person's sister

n a female person who is a fellow member of a sorority or labor union or other group

“none of her sisters would betray her”
(Roman Catholic Church) a member of a lay sisterhood (one of several founded in the Netherlands in the 12th and 13th centuries); though not taking religious vows the sisters followed an austere life
Type of:
fellow member, member
one of the persons who compose a social group (especially individuals who have joined and participate in a group organization)

n (slang) sometimes used as a term of address for attractive young women

babe, baby
Type of:
fille, girl, miss, missy, young lady, young woman
a young woman

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