ĝustigi

Decode it and there is nothing left to learn.Ĝusta at rank 301 is correct or exact, -ig- means to make something so, and ĝustigi is therefore to make a thing right. You set a watch, take in a sleeve, tune an instrument, correct an aim. The passive twin is ĝustiĝi, to come right by itself, and ĝustigo is the adjustment as a noun.

Where it stops and korekti starts. English uses correct for both jobs and Esperanto does not. Korekti at 1,310 operates on an ERROR: you correct a mistake, an exam paper, a spelling, somebody who has just said something false. Ĝustigi operates on a THING that is out of true: a clock running fast, a picture hanging crooked, a plan that no longer fits the week. Nobody made a mistake for a watch to need ĝustigi. Get this pair the wrong way round and you produce a sentence about correcting your wristwatch's moral failings, which is funnier than it is clear.

The -ig- machine is the point of the word. Attach it to an adjective and you get "make it that": beligi (make beautiful), pligrandigi (enlarge), klarigi (make clear, hence explain). Ĝustigi is simply the most useful member of a family you can extend yourself, which is why Esperanto never needed a separate verb for adjust, regulate, rectify, tune and set - it has one, and you already knew the root.