cusp
UK[kʌsp]US[kʌsp]
n
a pointed end where two curves meet, such as the point of a crescent moon or a tooth.
n
a point of transition between two different states, especially an important moment when a decision must be made.
Etymology
the word 'cusp' entered english in the late 16th century, directly from the latin 'cuspis', meaning 'point' or 'spear'. the latin term itself is of uncertain origin, though it may be related to the greek 'spithamē' (span, hand's breadth), hinting at a possible indo-european root connected to a sharp, projecting object. the initial concrete meaning of a pointed end, as on a tooth or a geometric figure, logically extended to the figurative sense of a decisive turning point or threshold, where one 'points' toward a new condition. this evolution captures the essence of a cusp as the precise tip from which change emanates.
Analysis
this word is a simplex loanword from latin. it is not productively formed from smaller, recognizable morphemes within modern english spelling.
Examples
the spacecraft was launched at the cusp of dawn.
her career is on the cusp of a major breakthrough.
the cusp of the molar tooth was worn down.