- 1[uncountable, countable] the process of using information you have in order to understand a particular situation or to find the answer to a problem He arrived at the solution by a simple process of deduction. If my deductions are correct, I can tell you who the killer was. We can examine the bones of dinosaurs and make deductions about how they lived. see deduce compare induction
- 2[uncountable, countable] the process of taking an amount of something, especially money, away from a total; the amount that is taken away deductions from your pay for taxes, etc. tax deductions
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