【医】 孪晶

Twin \Twin\, a. [OE. twin double, AS. getwinne two and two, pl.,
twins; akin to D. tweeling a twin, G. zwilling, OHG.
zwiniling, Icel. tvennr, tvinnr, two and two, twin, and to
AS. twi- two. See {Twice}, {Two}.]
1. Being one of two born at a birth; as, a twin brother or
sister.

2. Being one of a pair much resembling one another; standing
the relation of a twin to something else; -- often
followed by to or with. --Shak.

3. (Bot.) Double; consisting of two similar and corresponding
parts.

4. (Crystallog.) Composed of parts united according to some
definite law of twinning. See {Twin}, n., 4.

{Twin boat}, or {Twin ship} (Naut.), a vessel whose deck and
upper works rest on two parallel hulls.

{Twin crystal}. See {Twin}, n., 4.

{Twin flower} (Bot.), a delicate evergreen plant ({Linn[ae]a
borealis}) of northern climates, which has pretty,
fragrant, pendulous flowers borne in pairs on a slender
stalk.

{Twin-screw steamer}, a steam vessel propelled by two screws,
one on either side of the plane of the keel.