cleft

An opening, fissure, or V-shaped indentation made by or as if by splitting.

The river flows through a cleft in the mountains.

Then came some palsied oak, a cleft in him / Like a distorted mouth that splits its rim / Gaping at death, and dies while it recoils.

A piece made by splitting.

a cleft of wood

A disease of horses; a crack on the band of the pastern.

To syntactically separate a prominent constituent from the rest of the clause that concerns it, such as threat in "The threat which I saw but which he didn't see, was his downfall."

This may be so because in most languages the most natural clefting involves NP's, and it is in fact hard in most languages to cleft the verb, although some — notably Kwa languages in West-Africa — allow such clefting.

When the affected object is clefted, the clefted constituent may be assigned a contrastive reading on the event denoted by the clause, as is shown in (62).

split, divided, or partially divided into two.