varying

vaihteleva (present participle of)
puhekieltä A kind of variable, used by a fragment shader, that interpolates values across a primitive, so as to produce gradient effects etc.
2012, Patrick Cozzi, Christophe Riccio, OpenGL Insights

Another consideration to the relationship between vertex and fragment shaders is that adding too many additional varyings can be a drag on performance since they must all be interpolated (..)