Tooth Thickness and Space Width:

Tooth thickness is the thickness of tooth measured along with the space width and pitch circle is the space among two consecutive teeth deliberate along the pitch circle. They are equivalent to each other and compute half of circular pitch.

Top Land and Bottom Land

Top land is the top surface of and the bottom and the tooth land is the bottom surface among the adjacent fillets.

Face and Flank:

Tooth surface among the top land and pitch surface is known as face while flank is tooth surface among the bottom land and pitch surface.