v.
 take away (a number or amount) from another to calculate the difference. 
▸remove (a part of something).
 
  Derivative
  
    - subtracter 
(also subtractor)
 n.
  - subtraction n.
  - subtractive adj.
 
   
  Etymology
  C16 (earlier (ME) as subtraction): from L. subtract-, subtrahere ‘draw away’.