See more synonyms for twin on
  1. either of two children or animals brought forth at a birth.
  2. either of two persons or things closely related to or closely resembling each other.
  3. twin bed.
  4. Also called twin room. a type of hotel accommodation with twin beds, for occupancy by two persons.Compare double(def 13).
  5. Also called hemitrope. Crystallography. a compound crystal consisting of two or more parts or crystals definitely oriented each to the other; macle.
  6. Twins, Astronomy, Astrology. the constellation or sign of Gemini.
  1. being a twin or twins: twin sisters.
  2. being two persons or things closely related to or closely resembling each other.
  3. being one of a pair; identical: a twin bracelet; a twin peak.
  4. consisting of two similar parts or elements joined or connected: a twin vase.
  5. Botany, Zoology. occurring in pairs; didymous.
  6. Crystallography. of the nature of a twin; hemitrope.
  7. twofold or double.
verb (used with object), twinned, twin·ning.
  1. to bring together in close relationship; pair; couple.
  2. to furnish a counterpart to or a replica of; match.
  3. Informal. to divide or convert into two, parts, similar items, etc.: The old movie palace will be twinned, making two smaller theaters.
  4. Informal. to link or combine with: The new grocery store is twinned with a restaurant.
  5. Crystallography. to form into a twin.
  6. Obsolete. to give birth to as twins.
verb (used without object), twinned, twin·ning.
  1. to give birth to twins.
  2. to be paired or coupled.

Origin of twin

before 900; Middle English; Old English twinn (adj.), getwinn (noun and adj.); akin to Old Frisian twīne, Old Norse tvinnr double, Gothic twaihnai
Can be confusedtwain twin twine


verb (used with or without object), twinned, twin·ning. Scot.
  1. twine2. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for twin

Contemporary Examples of twin

Historical Examples of twin

  • They are twin plants of the forest, and are identified with its growth.

    Maid Marian

    Thomas Love Peacock

  • That I had but eyes, to look upon these twin invaders of domestic peace!'

    Barnaby Rudge

    Charles Dickens

  • In the end a pair of twin lights were seen perched on the summit.

    Homeward Bound

    James Fenimore Cooper

  • Had not their twin brotherhood drunk life from the same source?


    Emile Zola

  • There I left her too, for I wanted to see what the twin mice were about.

    Five Mice in a Mouse-trap

    Laura E. Richards

British Dictionary definitions for twin


    1. either of two persons or animals conceived at the same time
    2. (as modifier)a twin brother See also identical (def. 3), fraternal (def. 3)
    1. either of two persons or things that are identical or very similar; counterpart
    2. (as modifier)twin carburettors
  1. Also called: macle a crystal consisting of two parts each of which has a definite orientation to the other
verb twins, twinning or twinned
  1. to pair or be paired together; couple
  2. (intr) to bear twins
  3. (intr) (of a crystal) to form into a twin
  4. (intr) archaic to be born as a twin
  5. (tr)
    1. to create a reciprocal relation between (two towns in different countries); pair (a town) with another in a different country
    2. (intr)(of a town) to be paired with a town in a different country
Derived Formstwinning, noun

Word Origin for twin

Old English twinn; related to Old High German zwiniling twin, Old Norse tvinnr double
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for twin

Old English twinn "consisting of two, twofold, double," probably ultimately from Proto-Germanic *twinjaz (cf. Old Norse tvinnr, Old Danish tvinling, Dutch tweeling, German zwillung), from PIE *dwisno- (cf. Latin bini "two each," Lithuanian dvynu "twins"), from *dwi- "double," from root *dwo- "two" (see two). The verb meaning "to combine two things closely" is recorded from late 14c. The noun developed from Old English getwinn "double."

Online Etymology Dictionary, © 2010 Douglas Harper

twin in Medicine


  1. One of two offspring born at the same birth.
  1. Being two or one of two offspring born at the same birth.
  2. Consisting of two identical or similar parts; double.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

twin in Science


  1. One of two offspring born of a single gestation. Identical twins result from the division of a fertilized egg. Fraternal twins result from the fertilization of two separate eggs at the same time.
  2. A crystal structure consisting of two intergrown crystals that are mirror images of each other. Mineral twins can form as result of defective crystal growth in response to stress from rock deformation or during magma cooling.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.