1. countable noun A deduction is a conclusion that you have reached about something because of other things that you know to be true. [+ about] ⇒ It was a pretty astute deduction. ⇒ My mother had consequently made her own shrewd deductions about what was going on in my marriage. 2. uncountable noun
Deduction is the process of reaching a conclusion about something because of other things that you know to be true. ⇒ ...a case that tested his powers of deduction.
3. countable noun A deduction is an amount that has been subtracted from a total. ⇒ ...your gross income (before tax and National Insurance deductions). ⇒ After deductions for war reparations, the balance would be used to buy food and humanitarian supplies. 4. uncountable noun
Deduction is the act or process of subtracting an amount of money from a total amount. ⇒ After the deduction of tax at 20 per cent, the interest rate will be 6.2 per cent.
COBUILD Advanced English Dictionary. Copyright © Harper Collins Publishers