Drawdown
Peak-to-trough percentage decline in account equity. The most honest measure of strategy risk.
Max drawdown is the pain threshold you need to sit through. Most retail can handle 5%, lies about 15%, quits at 25%. Funded programs hard-fail at 10%. Size strategies so max expected drawdown is well below your real quitting point.
Related
Learn to actually use Drawdown.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.