pho·to·taxis \“+\noun alsopho·to·taxy\ˈfōd.əˌtaksē\ (pluralphototax·es \-|takˌsēz\ ; orphototax·ies \-ˌtaḵsēz\) Etymology: New Latin, from phot- + -taxis : a taxis in which light is the directive factor (as in the movement of an infusorian toward the lighted side of a vessel); also: the orientation of various chloroplasts to light