It’s “losing” not “loosing”
Given the Internet's fond dismissal of grammatical norms and conventional rules, perhaps it shouldn't be surprising that correct spelling and rules of grammar appear so easily discarded these days, but spelling and grammar do still matter. To that end, allow me to comment on "losing" vs "loosing", "lose" vs "loose", and "loser" vs "looser".
First of all, the words losing and loosing are both real words, which is probably why most spell-checkers ignore the faux-pas of mistaking one for the other. However, they mean completely different things, and are not in any way interchangeable. In the same way, "lose" and "loose", along with "loser" and "looser" are also completely unrelated to each other.
The short video above will provide you with more information on the same subject, but the "in a nutshell" version is below.
Okay, so probably the most common error among these words is incorrectly using loose instead of lose, and loosing instead of losing, followed closely by mistakenly using looser for loser.
Let's be clear, the terms loosing, looser, and loose have nothing whatsoever to do with loss, or "not winning". They're completely unrelated. Yes, they are all words, but they mean something different.
If you want to use any of these words to refer to "not winning" or loss of some kind, then you'll be wanting to use lose, losing, loses, and loser.
Okay, lets provide a few examples of how each of the words should be used correctly.
Lose: (i.e. opposite of win; opposite of find; related to loss of some kind)
a) If I lose the game then I will be disappointed.
b) I hope I don't lose any money playing poker.
c) I'm sure the soccer team will lose tomorrow.
Losing: (i.e. opposite of winning; opposite of finding; related to loss of some kind)
a) The losing team buys pizza after the game.
b) I really don't like losing; it's not much fun.
c) Do you think I'm crazy? I think I'm losing my mind.
Loses: (i.e. opposite of wins; opposite of finds; related to loss of some kind)
a) The player who loses must go home afterwards.
b) Peter loses money when he gambles.
c) If your team loses then my team will be champions.
Loser: (i.e. opposite of winner; opposite of finder; related to loss of some kind)
a) Unfortunately, in most games, there is always a winner and a loser.
b) Although you have made many mistakes, you are not a loser.
c) The loser of this semi-final will play the loser of the other semi-final for third-place.
[spacer height="20px"]It's in these types of example where people often seem to go astray and use the wrong word, but hopefully you can now see how these words are correctly used. And, hopefully you'll notice that there isn't a double "o" in sight. As already noted, if you're referring to loss, or "not winning" then lose, losing, loser and loses are almost certainly the words you should be using.
Nonetheless, as mentioned at the beginning, all of the words (i.e. losing, loses, loser, lose, loosing, looses, looser and loose) are real words, it's just that they often get used incorrectly. So, some examples of the remaining words. And note, these "double o" words have nothing at all to do with "not winning" or any kind of loss.
Loose: (i.e. not tight)
a) I accidentally set the chickens loose when I forgot to shut the gate.
b) My jeans are very loose since I lost weight.
c) It's best to tighten a screw if you see it is loose.
d) Do you have any loose change you can spare?
e) Watch out! There are lions on the loose!
f) The police will set loose their canines if the rioters continue.
Looser: (i.e. less tight)
a) The looser rocks tumbled down the cliff to the beach.
b) Can you do something to make the lid looser? It's too tight!
c) Your clothes seem much looser since you started your diet.
Looses: (i.e. set free, lose grip)
a) The security guard looses the dogs at night, and they roam freely.
b) The hunt master looses the hounds when a fox appears.
c) Jack's grip on the rope looses as he becomes tired; soon he'll die.
Loosing: (i.e. setting free, losing grip)
a) The best part of the hunt is the loosing of the hounds.
b) The freezing cold bit Jack's hands, and his grip on the rope was loosing.
c) Neville likes loosing the hungry dogs whenever someone tries to climb the fence.
[spacer height="20px"]The examples provided are certainly not exhaustive, and there are several other variations of the words that didn't even get a mention, but hopefully you can now understand the difference between the most common spellings.
The most confusion for people seems to come when they're trying to refer to "not winning" in some way (i.e. lose, losing, loser, loses), but just remember that in all of those cases there is never a double "o".
I hope this helps at least a few people, but the video above will also give you lots of assistance too. Good luck with your learning!