Identical twins Mark and Scott Kelly, both former NASA astronauts.



  • Either of two people (or, less commonly, animals) who shared the same uterus at the same time; one who was born at the same birth as a sibling.
  • Either of two similar or closely related objects, entities etc.
  • A room in a hotel, guesthouse, etc. with two beds; a twin room.
  • A twin size mattress or a bed designed for such a mattress.
  • A two-engine aircraft.
  • A twin crystal.


  • To separate, divide.
  • To split, part; to go away, depart.
  • To join, unite; to form links between (now especially of two places in different countries); to pair with.
  • To give birth to twins.
  • To be, or be like, a twin to (someone else); to match in some way.
  • To be, or be like, a pair of twins (for example, to dress identically); to be paired or suited.


  • Double; dual; occurring as a matching pair.
  • Forming a pair of twins.


Similar words


  • From Middle English twinne, twynne, from Old English ġetwin, ġetwinn and twinn, from Proto-Germanic *twinjaz, *twinaz, from Proto-Indo-European *dwino- ("twin"), from *dwóh₁. Cognate with Scots twyn ("twin"), Dutch tweeling ("twin"), German Zwilling ("twin"), Swedish tvilling ("twin"), Faroese tvinnur ("a double set"), Icelandic tvenna ("duo, pair"), Lithuanian dvynys ("twin"), Russian двойня ("twin").
  • From Middle English *twin, *twyn, from Old English twin, twinn, from Proto-Germanic *twīhnaz, from Proto-Indo-European *dwóh₁. Cognate with Icelandic tvennur, Gothic 𐍄𐍅𐌴𐌹𐌷𐌽𐌰𐌹.

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