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 Put Option?83 Views
finance a la shmoop what is a put option? hot potato hot potato
ow ow! yeah remember that game well nobody wanted the potato, poor thing. the
players wanted to put it in someone else's hands. well put options kind [glue put around a flaming potato]
of work the same way. a put option is the right or option or choice to sell a
stock or a bond at a given price to someone by a certain end date.
all right example time. you bought netflix stock at the IPO a zillion years
ago at $1 a share. that's you know splits adjusted. all right now it's a hundred
bucks a share. if you sell it you pay taxes on a gain of 99 dollars a share. in
California that would be a tax of something like almost 40 bucks. well the
stock was a hundred but you keep only something like 60. feels totally unfair.
right so you really don't want to sell your stock but you're nervous about the [graph shown]
next few months that Netflix will crater for a while and go down ten
maybe twenty dollars. longer term though you think it'll hit 300. so this is the
perfect setup to maybe look at buying some put options on Netflix. if the stock
goes down your put options go up. with Netflix volatile but at a hundred bucks
a share ,you look up the price of an $80 strike price put option expiring in
December, and you know that's mid-september now .for five bucks a share
you can protect your stock for the next few months .think about it like temporary [stocks placed in vault]
term life insurance. you pay the five dollars a share in the stock goes down
to 82 by mid December, worst of all worlds. well not only did you lose the $5
a share but your stock has lost $18 in value. but had Netflix really cratered
and gone to say $60 a share well you would have exercised your put and sold
your shares at 80 bucks. well those put options you paid $5 for
would be been worth 15 bucks a share. in buying that put option you've [equation shown]
guaranteed that your loss will be no more than a $75 value for your Netflix
position at least for that time period and ignoring taxes. well remember that
options expire after December whatever like the third Friday of the month it's
usually when options expire, you then have no protection and your shares float
along naked. naked? really who knew accounting could get so [paper put option goes "skinny dipping".]
raunchy. yeah well that's naked put options.
that's what they really are people.
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