Loose means not tight, not closely constrained or constricting. Loose is mainly an adjective used to describe things that are not tightly fitted. Where it is a verb, it means to release.
Lose means to misplace something or cease to have either physically or in an abstract sense. It is only a verb. 'To lose' means to suffer loss or be deprived of something or fail to keep possession of.
One simple and interesting way to remember the difference between the two words is to think that "loose has lost an 'o'".
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