Put-call parity

Calls can be combined with forwards or with positions in the underlying asset and
the money market to construct synthetic puts with the same exercise price (and vice
versa). In the special case of European at-the-money forward options:
Ω The value of an at-the-money forward European call is equal to the value of
an at-the-money forward European put.
The reason is that, at maturity, the forward payoff equals the call payoff minus the
put payoff. In other words, you can create a synthetic long forward by going long one
ATM forward call and short one ATM forward put. The construction is illustrated in
Figure 1.7.