noun

1. a woman or girl as she is related to the other children of her parents: sometimes also used of animals
2. a woman or girl related to one by having a parent in common; half sister
3. a stepsister
4. a foster sister
5. a close female friend who is like a sister
6. a female fellow member of the same race, church, profession, organization, etc. sorority sister, soul sister
7. a member of a female religious community, usually one with simple vows
8. something associated with another of the same kind, model, etc.
9. Brit. a nurse, esp. a head nurse
10. Informal any woman: often used as a familiar term of address

Etymology: ME < ON systir (akin to OE sweoster > dial. suster), akin to Ger schwester < IE *swesor-, sister (> Sans svasar, L soror, OIr siur) < *sewe-, (one's) own, refl. pron. (see suicide) + *sor-, woman: hence, lit., woman of our (family)

adjective