See: Theta Decay.
It sounds like what happens when you don't floss, but it actually refers to the way that the time value of a stock option decays or declines with time.
The closer to the expiration date, the smaller the time value of the option. (Time value: as in...if you had an option to buy KO for $50 when KO is today trading at $42, and that option expired in 2 weeks, it probably wouldn't be worth much, because the odds of KO trading much above $50 in the next 2 weeks is relatively low. But if you had Theta (or time) of 3 years before the option expired, then yeah, that option could be worth a ton.)
Example:
You sold puts on GOOG at $450 for $35 which expire in 4 months. The stock today is at $600. That is, you sold the right for someone to make you buy shares of GOOG at $450 any time between now and 4 months from now for 35 bucks. Things go along and, well, GOOG just stays pretty flat, doing a whole lot of nothing.
It's now 3 days before those put options expire (we've gone 3.9 months with a whole lot of nothing happening in GOOG). The stock is still around $600 a share. What are the odds it plummets $150+ in 3 days? Really low. So the value of those puts is almost fully expired—its Theta has decayed to just 3 days' worth of trading time, and it is highly likely you just collect your 35 bucks, walk away, and buy yourself a really nice burger at a Manhattan eatery.
Related or Semi-related Video
Finance: What Is a Call Option?25 Views
finance a la shmoop. what is a call option? option? option, where are you? okay
yeah yeah. not phone options, call options. and a close but no cigar. a call option [man smokes in a tub of cash]
is the right to call or buy a security. the concept is easy the math is hard.
you think Coca Cola's poised for a breakout as they go into the new low
calorie beverage business. their stock is at 50 bucks a share and you can buy a [man stands on a stage as crowd cheers]
call option for $1. well that call option buys you the right
to then buy coke stock at 55 bucks a share anytime you want in the next
hundred and 20 days. so let's say Coke announces its new sugarless drink flavor
zero it's two weeks later and the stock skyrockets to fifty eight dollars a
share. you've already paid the dollar for the option now you have to exercise it. [man lifts weights]
so you buy the stock and you're all in now for fifty five dollars plus one or
fifty six bucks a share and your total value is now fifty eight bucks. well you
could turn around today and sell the bundle that moment, and you'll have
turned your dollar into two dollars of profit really fast. and obviously had the [equation on screen]
stock not skyrocketed so quickly well you would have lost everything. still you
lucked out and now you're sitting on some serious cash, courtesy of your call [two men in a tub of cash]
options. as for Coke flavor zero turned out to be nothing more than canned water.
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