Cusp

Part of speech: noun

Pronunciation: /kʌsp/

Definitions

1. The point where two curves meet or a critical moment marking the transition between two different states
2. The location at which two distinct edges converge or a significant threshold signaling a change from one condition to another is recognized
3. A junction where opposing shapes intersect or a pivotal juncture indicating a shift from one circumstance to another is identified

Etymology: The word "cusp" began as a Latin term for a sharp point. In Latin, "cuspis" meant a point, spear, or pointed end, and it was first applied in astrology, where a cusp is the boundary between two of the twelve houses of the sky, the points at which one zone of influence gives way to another. That sense of a dividing point is the seed of the modern meaning. From the sharp tip of a spear or horn, the idea moved to the critical moment when one state gives way to another. A cusp, in the sense of a turning point, is the spot where things tip over, which is why the word fits so neatly with the astrological boundary it once named. "Cusp" is also a doublet of "cuspid," the term for a pointed tooth, and both come from the same Latin root, so the sharp-pointed image runs through the family of words.

Synonyms: edge, threshold, verge, border, brink

Antonyms: middle, center, interior, core, heart