To deduct means to subtract or take away an amount from a total. When your teacher deducts points from your test score for wrong answers, she's removing those points from what you could have earned. If you started with 100 possible points and got three questions wrong worth 5 points each, the teacher deducts 15 points, leaving you with 85.

The word appears often in math, but also in everyday situations. A store might deduct the value of a coupon from your bill. Your parents might deduct from your allowance if you skip your chores. Companies deduct expenses from their income to calculate profit: if they earned $1,000 but spent $300 on supplies, they deduct those expenses to find they made $700 in profit.

A deduction is the amount subtracted or the act of subtracting it. People often confuse deduct with deduce, but they're different: you deduct money (subtract it), while you deduce an answer (figure it out through reasoning).