Sister

A sister may be:

• Literally
  • a female member of a group of siblings in one family
  • a nun or other member of a female religious order
  • a member of a sorority
  • a female hospital nurse
  • a female member of a mutual organisation such as a trade union

• Metaphorically
  • one of a pair or larger group of similar things with established relations, such as sister cities, sister colleges, or sister companies under common ownership.

• The band Letters To Cleo made an album named Sister.

See also: Seven Sisters