Mortise and Tenon Dimension Labels and Names
There are three dimensions needed to make a mortise and tenon joint. However the names of these three dimensions change depending on which part of the joint you are measuring.
A: Tenon width and Mortise Length.
B: Tenon length and Mortise Depth
C: Tenon thickness and Mortise Width.
Understanding these names is important to understand when you are laying out matching parts of a joint.
Great Site for the beginner
Thanks John!