If something is derivable, you can work it out from something else you already have. A number, a fact, or an answer is derivable when the other information is enough; you do not need a new measurement, only a calculation or a careful step of thinking. Maths, science, and formal writing use it: the speed is derivable from distance and time. It is not a word for the bus stop. Nearby words can trip you: derived means you already got it from something; derivable means you can. A derivative is often the thing you got, or in maths a special kind of rate. Derivable stays with the idea 'this can be pulled out of that'.