Short

A bet that a price will fall. You sell shares you do not own, then buy them back later. If the price fell, you keep the difference. If it rose, you lose it, and a price can keep rising, so a short loss has no top limit. Here, a short sale sets aside 50% of the shares' value from your cash as margin, which comes back when you buy the shares back. A short position also owes any dividend paid on those shares while it is open. Selling an option you do not own, also called writing it, is short too: you keep the premium and owe the contract if it is settled. A call or put you wrote and do not cover with shares holds margin of 20% of the underlying's value.