sister - definition and synonyms

noun [countable] 

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  1. 1
    a daughter of your parents. A son of your parents is called your brother

    He has two brothers and two sisters.

    big/little sister (=an older or younger sister):

    She has to babysit for her little sister tonight.

     Synonyms and related words
  2. 2
    British a female nurse in charge of a hospital ward (=a room for people who are ill in a hospital)

    the day/night sister

    1. a.


      British used for talking to a sister in a hospital

      My leg is still hurting me, Sister.

  3. 3
    a nun (=a woman who is a member of a religious community)
    1. a.


      used in front of the first name of a nun, when talking to her or about her

      Sister Mary