Charm

Charm, also known as delta decay, measures the rate of change of an option delta as time passes toward expiration. It is a second-order sensitivity that accounts for the fact that an options delta is not static but evolves as the time to maturity decreases.

For a trader who is delta-neutral, charm represents the drift in the portfolio delta that occurs simply due to the passage of time. In high-frequency crypto trading environments, charm is significant because it dictates the natural unwinding or tightening of hedge positions as expiration approaches.

Understanding charm allows traders to predict how their delta will naturally evolve, enabling them to schedule rebalancing more efficiently. It is particularly relevant for short-dated options where the impact of time decay on delta is most pronounced.

Failing to account for charm can lead to unintended directional exposure, potentially resulting in losses as the option nears its expiry. It is a vital component of automated risk management systems in modern electronic trading.