Margin
The collateral a broker requires to hold a leveraged position. The higher the exposure, the more margin is required to keep it open.
Definition
Margin is the collateral required to open and hold a leveraged position — not the “purchase price” of the whole instrument, only security against the exposure. If equity falls below the required margin, the result can be a margin call or a stop-out.
Example
You want exposure equivalent to 10,000 EUR on a currency pair. At 1:30 leverage the broker requires margin equal to a fraction of that notional — the rest is leverage. Your real risk is the price move times the size, not the margin you deposited.
Anti-example / common mistake
“I have 500 PLN of margin, so I am only risking 500 PLN.” No — with leverage the loss can approach the whole equity (and hit a stop-out faster) if the size is too large relative to the stop.