Main Entry: ¹twin

Pronunciation: \ˈtwin\

Function: noun

Etymology: Middle English, from twin twofold

Date: 14th century

1 a : either of two offspring produced at a birth b plural capitalized : gemini
2 : one of two persons or things closely related to or resembling each other
3 : a compound crystal composed of two adjoining crystals or parts of crystals of the same kind that share a common plane of atoms

— twin·ship \-ˌship\ noun