What is Bleach?

Bleach definition and meaning on Dictionary terms:
verb (used with object)
to make whiter or lighter in color, as by exposure to sunlight or a chemical agent; remove the color from.
Photography. to convert (the silver image of a negative or print) to a silver halide, either to remove the image or to change its tone.

verb (used without object)
to become whiter or lighter in color.

a bleaching agent.
degree of paleness achieved in bleaching.
an act of bleaching.