What happens if Delta is negative?

What happens if delta is negative depends on the field, but it generally means decrease, inverse movement, or loss. In general mathematics and science, a negative delta means the final value is less than the initial value. For example, if ΔT is negative, temperature dropped. If ΔH is negative in chemistry, the reaction is exothermic and releases heat to surroundings. If your profit delta is negative, you lost money. In finance and options trading, negative delta has a very specific consequence. Put options have negative delta, from -1 to 0. A -0.50 delta put means if the underlying stock goes up $1, the put loses about $0.50 in value, and if the stock goes down $1, the put gains about $0.50. A portfolio with net negative delta will profit when the market falls and lose when the market rises, so it is bearish. If you are long stock with delta +1 and you buy puts with negative delta, your overall delta becomes less positive, reducing risk. In physics, negative delta velocity means deceleration. In business, negative delta between actual and target means underperformance. So negative delta does not mean something broke. It simply indicates direction. Positive delta means up or same direction, negative delta means down or opposite direction. You must look at whether negative is expected or desirable for your goal.