Definition of "eosin"

Thus the fluorescence of the familiar dye eosin can be excited quite well by ultra-violet or short-wave blue light, but is much better excited by visible green light with a wavelength close to that of the emitted radiation.

1999, Dan J. Goldstein, Understanding the Light Microscope‎, page 91

Eosins are acid xanthene or phthalein dyes. Eosin Y, eosin B, phloxine and erythrosin (which unlike other eosins, is halogenated with iodine), are the common members of this group of dyes.

2000, J. Ochei, A. Kolhatkar, Medical Laboratory Science: Theory And Practice, page 450

The hematoxylin and eosin stain (H&E) is the most widely used histological stain.

2012, John D. Bancroft, Christopher Layton, “10: The hemotoxylins and eosin”, in S. Kim Suvarna, Christopher Layton, John D. Bancroft, editors, Bancroft's Theory and Practice of Histological Techniques, 7th edition, page 173