Definitions for "Greyscale"
Keywords:  grey, shades, photography, black, tonal
From Portable Network Graphics (PNG) Specification (Second Edition) ( 2003-11-10) image representation in which each pixel is defined by a single sample of colour information, representing overall luminance (on a scale from black to white), and optionally an alpha sample (in which case it is called greyscale with alpha).
A greyscale or grayscale (depending on which continent you're on) image is made up of different percentage of blacks, from 0% or white, to 100% or pure black. You can also say it's the tonal scale of grey.
An image made up of multiple grey values.
Is the color of gray over different intensity levels. Calibration of this requires an accurate color measurement tool. These include optical comparators, spectra radiometers and color analyzers.