Stones in these grades will "face up" colourless (i.e., slight traces of colour will not be apparent in mounted stones to other than the trained eye).
Small stones in this range will "face up" colourless when mounted but larger stones will be tinted.
Mounted stones in these grades will display a yellowish tint even to the untrained eye
Taken from http://www.ags.org/public/howtobuy/chart.htm
Inclusions are difficult to locate or see under 10X magnification.
Inclusions present less difficult to locate or see under 10X magnification.
Inclusions are readily seen at 10X magnification, although they remain invisible to the unaided eye when the diamond is viewed face up.
One or more inclusions, or their effect, can be seen by the unaided eye.
Inclusions are easily visible to the unaided eye.
Inclusions are so obvious and large that they effect both the brilliancy and beauty of the diamond.
Shattered appearance or vivid disfiguring and dangerous inclusions and surface marks.