the.com/expert

Someone who has made every mistake available in a narrow enough field to notice.

means Someone with deep, demonstrated knowledge or skill in a particular field, usually earned through experience.

from From Latin 'expertus,' the past participle of 'experiri' meaning 'to try, test, prove.' It's a cousin of 'experience' and 'experiment' — all three share that same root of testing things out. The sense drifted over time from 'one who has tried something' to 'one who has tried it enough to be trusted at it.'

10,000-hour myth
Original study never claimed a universal magic number.
narrow scope
Experts often fail badly outside their specific niche.
overconfidence risk
Experts can be more confidently wrong than novices.
shared root
Expert and experiment both come from trying things.
the.com · every word