The story
Introduced by Morgan A. Hanson in 1981 as a generalization of convex.
Etymology from Wiktionary, CC BY-SA 4.0.
invex
Today it means: Of a differentiable function f:ℝⁿ→ℝ, being such that there exists a vector valued function g such that f(x)-f(u)≥g(x,u)·∇f(u),, for all x and u. Full definition →