-tropic, suffix
(ˈtrɒpɪk, ˈtrəʊpɪk)
[f. Gr. τροπή turning (n.) + -ic.]
Forming adjs. with the senses: (a) ‘turning or attracted towards’, as in geotropic, heliotropic, sympathicotropic adjs.; (b) ‘affecting’, as in neurotropic, psychotropic adjs. (in epithets of hormones used interchangeably with -trophic, q.v.).