twinning

The bearing of twins.

A pairing or union of two similar or identical objects.

The formation of twin crystals.

The process or state of being twinned: said of crystals. See twin, n., 3.

Separation; parting.

The assemblage of two or more crystals, or parts of crystals, in reversed position with reference to each other in accordance with some definite law; also, rarely, in artificial twinning (accomplished for example by pressure), the process by which this reversal is brought about.

repeated twinning of crystal lamellæ, as that of the triclinic feldspars.

twinning of more than two crystals, or parts of crystals.

See the Note under Twin, n.