<p>Theta (Θ) in options trading represents the rate at which the price of an option changes as time passes. It is a crucial component of the 'Greeks' family, a set of metrics used to measure and manage the risk of options trading.</p>

<h2>How It Works</h2>
<p>Theta is often referred to as 'time decay' because it quantifies how much an option's price will decrease with the passage of each day. It is typically expressed as the change in the option's price for a one-day change in time to expiration, holding all other factors constant. Theta is always positive for call options and negative for put options, meaning that as time passes, call options lose value while put options gain value.</p>
<p>For example, if an option has a theta of -0.05, it means that the option's price will decrease by $0.05 for each day that passes until expiration, all else being equal.</p>

<h2>Why It Matters</h2>
<p>Understanding theta is vital for options traders as it helps them anticipate how the price of an option will change over time. This is particularly important for strategies that involve holding options for extended periods, such as covered calls or protective puts. Traders can use theta to their advantage by buying options that are expected to experience significant time decay, or by selling options to collect the theta premium.</p>
<p>Moreover, theta is not constant and can change rapidly, especially as an option approaches expiration. This is because the rate of time decay accelerates as expiration approaches, a phenomenon known as 'theta decay'. Therefore, traders must continually monitor and manage their theta exposure to mitigate potential losses.</p>