-tropic Also -tropous.
Turning; changing; affecting.
[Greek tropē, turn, turning.]
Adjectives in both these endings are closely related to nouns in -tropism and -tropy in their various senses. Examples include isotropic (Greek isos, equal), having a physical property which has the same value when measured in different directions; thixotropic (Greek thixis, touching), of a substance that becomes less viscous when subjected to an applied stress; psychotropic (Greek psukhē, breath, soul, mind), denoting drugs that affect a person's mental state.
Adjectives in -tropous have a similar sense, but are much less common; two examples are orthotropous (Greek orthos, straight, right), of an ovule, part of the ovary of the plant, that is growing straight; campylotropous (Greek kampulos, bent), having an ovule that is partially inverted and curved.