Tacit knowledge
noun
Understanding learned by doing a task alongside someone who already knows it. It is the part that never quite makes it into the manual.
Also known as know-how, practical knowledge
Tacit knowledge is the understanding built by doing the work beside someone who already knows how. It is not the procedure in the manual. It is the reason the experienced person knows the procedure will fail on this particular Tuesday.
You learn it in the gap between the written rule and the live situation: what a client’s silence means, when a spreadsheet that balances still smells wrong, which problem needs escalating before the dashboard turns red.
This is why the disappearance of junior work creates a problem larger than fewer entry-level jobs. The repetitive task was also the room where judgement travelled from one generation to the next. Tacit knowledge does not transfer neatly in a document. It passes through shared work.