[eo.sin] also eo.sine n [ISV, fr. Gk eos dawn] (1866) 1: a red fluorescent dye obtained by the action of bromine on fluorescein and used esp. in cosmetics and as a toner; also: its red to brown sodium or potassium salt used esp. as a biological stain for cytoplasmic structures
2: any of several dyes related to eosin