Abundant is a number for which the sum of all its proper factors is greater than the number itself.Deficient is a number for which the sum of all its proper factors is less than the number...
you dont have enough b12. take some. either in a suppliment or eat foods that contain it
The only one I can think of is 'hypo'.
Deficient means something lacks something. "This meal is deficient in protein" means it lacks protein.
It has incomplete octet (incomplete valence shell) after bond formation.