期权卖方赚钱法宝—希腊字母Theta
期权卖方（Call Seller/Writer）是指卖出期权合约的一方。可以卖出的标的物有：认购期权（看涨期权）和认沽期权（看跌期权）。开仓卖出期权通常称为建立期权空头（Options Short）头寸。针对期权卖方来说，主要的盈利方式是赚取“时间价值”，针对时间价值，期权中用Theta来计算。
无论看涨期权还是看跌期权，随着时间的流逝价值都会逐渐下降。Theta主要是测量时间变化对期权价值的影响。表示时间每经过一天，期权价值会损失多少。一般在期权软件上都是显示期权价值每日下降的点数。如果告诉你一个期权的Theta是-0.06，就表示在其他条件不变的情况下，期权价格会每天下降0.06，如果期权今天的价值是9.06，那么明天期权的价值就是9。随着到期日的临近，时间价值损耗会加速。Theta以非线性方式影响期权价值。
Theta的正负该如何理解？
跟之前的希腊字母Delta，Gamma一样，先看Theta的符号。显然从定义上看，Theta表示的是期权价值随时间的损失，所以对期权的买方来说，Theta值一般写成负值，而对于期权的卖方来说，天然赚取时间价值的钱，所以写成正的。
当你选择作为期权买方，就选择了对抗自然规律—与时间损耗为敌，必须克服其对期权价格的下拉作用。这张合约从诞生之日起，直至到期，每一天期权的外在价值都在减少。这就好比一辆装满河沙的卡车，在开往目的地的途中，不断将沙子漏在地上。如果我们把这些「沙子」全部拾起,算一个总数，会发现刚好等于期权合约的外在价值。而卖方恰恰赚的正是这些每天不断漏在地上的沙子。
作为期权买方,拥有了正Gamma,且损失一开始就是确定的(风险兜底) ,但它的Theta却为负数。作为期权卖方,虽然是负Gamma,损失可能会很大(风险开口），但却拿到了正Theta，利用时间损耗赚钱。
Theta与到期日和执行价的关系
执行价方面，平值期权附近的Theta读数最大，而分别往两边,进入ITM或OTM状态，Theta都在逐渐缩小。
随着到期日临近，如果期权合约处在平值状态附近，Theta曲线会被逐渐抬高，Theta读数增大。如果期权合约处在深度OTM或深度ITM状态，Theta曲线会被逐渐压低，趋近于X轴，Theta读数缩小。
这意味着越靠近到期日，靠近平值状态的期权的外在价值会加速衰减。而深度的实值或虚值状态，外在价值衰减的速度反而慢了下来。
Theta与波动率
Theta还和一个重要因素有直接关系，这个因素便是波动率。期权卖方总是想要在波动率高的时候卖期权，也是因为波动率和期权的Theta绝对值成线性正比。这意味着，波动率越高，期权的Theta绝对值便越大，越有利于卖方赚取时间值。
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