Definitions

1. noun

a dye or substance used to colour or stain a surface in addition to the primary stain, especially in histology, to differentiate cell components or to mask background staining.

“The researcher applied a counterstain to the sample to enhance the visibility of the cells.”

2. verb

to stain or colour (a surface or substance) with a dye or substance, especially in addition to a primary stain, in order to differentiate cell components or to mask background staining.

“The technician counterstained the sample to reveal the presence of certain cell structures.”