Coexpression is a derived term of coexpress.

In genetics|lang=en terms the difference between coexpression and coexpress

is that coexpression is (genetics) the simultaneous expression of two or more genes while coexpress is (genetics) to express together with another gene.

As a noun coexpression

is (genetics) the simultaneous expression of two or more genes.

As a verb coexpress is

(genetics) to express together with another gene.