What is the difference between Abnormal and Subnormal?

What is the difference between Abnormal and Subnormal? : 
Abnormal 

( 1 ) Different (in an undesirable way) form what is normal or ordinary or expected

Is he mentally abnormal? 

Subnormal 

( 1 ) Below normal – less than normal

Subnormal temperature does not suit my health. 

( 2 ) Below the normal level of intelligence

He was a subnormal child.