Deductible is about taking an amount off a larger amount — money, almost always. As an adjective, a deductible cost is one the rules let you subtract. Tax is the usual place: if a cost is tax-deductible, you may take it off before tax is calculated, so you pay tax on a smaller number. A cost that is not deductible has to stay in the total. As a noun, especially with insurance, the deductible is the first chunk you pay yourself. If a repair costs a lot and your insurance has a deductible of a certain amount, you pay that first piece, and the company pays some or all of the rest. A higher deductible usually means a cheaper monthly bill, but a nastier surprise when something goes wrong. You will see this word on tax forms and insurance letters. In a market, people just say “take off” or “subtract.”