| ̷ ̷ ̷ ̷+ noun
or merocyanine dye
Etymology: mer- (III) + cyanine
: any of a class of polymethine dyes that are used like the cyanine dyes as sensitizers in photography but differ from the cyanine dyes in containing an acidic heterocyclic nucleus (as rhodanine or pyrazolone) linked to a basic heterocyclic nucleus (as quinoline or benzothiazole) and in not being ionized