|1.||a. either of two persons or animals conceived at the same time|
|b. identical See also fraternal (as modifier): a twin brother|
|2.||a. either of two persons or things that are identical or very similar; counterpart|
|b. (as modifier): twin carburettors|
|3.||Also called: macle a crystal consisting of two parts each of which has a definite orientation to the other|
|—vb , twins, twinning, twinned|
|4.||to pair or be paired together; couple|
|5.||(intr) to bear twins|
|6.||(intr) (of a crystal) to form into a twin|
|7.||archaic (intr) to be born as a twin|
|a. to create a reciprocal relation between (two towns in different countries); pair (a town) with another in a different country|
|b. (intr) (of a town) to be paired with a town in a different country|
|[Old English twinn; related to Old High German zwiniling twin, Old Norse tvinnr double]|
One of two offspring born at the same birth. adj.
Being two or one of two offspring born at the same birth.
Consisting of two identical or similar parts; double.
|twin (twĭn) Pronunciation Key
either of two young who are simultaneously born from one mother. Twinning, common in many animals, is of two biological kinds: the one-egg (monozygotic), or identical, type and the two-egg (dizygotic), or fraternal, type. The latter type is more usual and can be thought of simply as a litter of two. In humans, psychological studies of sets of identical twins, since they are genetically identical, have provided much otherwise unobtainable information on the relative effects of genetic endowment and environment. See also multiple birth.
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