subtract

Concise Oxford English Dictionary © 2008 Oxford University Press:
subtract/səbˈtrakt/

▶verb take away (a number or amount) from another to calculate the difference.

■ remove (a part of something).

– derivatives
subtracter (also subtractor) noun,
subtraction noun,
subtractive adjective.

– origin C16 (earlier (ME) as subtraction): from L. subtract-, subtrahere ‘draw away’.