- noun one of two babies or animals born at the same time from two ova fertilised at the same time or from one ovum that splits in two
- noun one of two babies born to a mother at the same time
- adjective fitted as a pair
- verb to make a special arrangement between a town in one country and one of similar size or situation in another, involving visits between the two places
Origin & History of “twin”
Twin originally meant simply ‘double’, but the specific application to ‘two people born at the same birth’ had already evolved by the end of the Old English period. The word goes back via prehistoric Germanic *twisnaz to Indo-European *dwisno-, a derivative of the base *dwi- ‘double’ (other derivatives formed with the same -n suffix include English between and twine (OE) – etymologically thread of ‘two’ strands).