Put Call Parity
Put call parity is a fundamental relationship in options pricing that links the price of a European call option, a European put option, the underlying asset, and the risk-free bond. It states that the cost of a portfolio containing a long call and a short put must equal the cost of a long position in the underlying asset minus the present value of the strike price.
If this relationship is violated, an arbitrage opportunity exists, allowing traders to buy the cheaper side and sell the more expensive one. This principle is vital for maintaining market efficiency and for deriving the price of one instrument from the others.
It is a cornerstone of quantitative finance and ensures that derivative markets remain consistent with underlying asset prices.