Character of the tongue: Tongue color is lighter than normal.  The tongue iswhiter than redder.
Clinical significance: It indicates deficiency of qi and blood or deficiency of yang.
Main causes:
a. Insufficiency of qi and blood and subsequent tongue malnourishment.
b. Insufficiency of yang failing to warm the blood and lift blood up to nourish thetongue.
c. Interior cold and contracture of the channels due to deficiency of yang failing to provide adequate blood to nourish the tongue.
Also learn Yuan-Qi.