# What does nonconvex multilinear mean?

I am not a math student so I am sometimes a bit confused when it comes to math lingo. For me non-convex would mean its concave which means functions have local minima in case of a minimization problem... In the paper I am working with genetic algorithms and tabu-search. I would figure the reason for the usage are the concave terms.

Am I on the right track of understanding?

This here is the non-convex contrain where z are the number of containers being unloaded and loaded.

Non-convex means not convex, which could mean concave but also neither convex nor concave, such as a bilinear term $$xy$$.