A lot of people are mixing up lose and loose. In particular, a lot of people are writing loose when they really mean lose. Here are the definitions of the two words from my Penguin dictionary:
loose [lOOs] adj not fastened or pre-packed; not tied up or confined; able to move freely; not tight, not firmly fixed; not close-fitting; careless, inaccurate, vague; dissolute, immoral; not closely woven; flabby; (of bowels) inclined to diarrhoea; l. box stable or van in which an animal can move about; at a l. end uncertain what to do next; unoccupied ~ loose adv in a loose way; play fast and l. behave rashly or unscupulously ~ loose n release; on the l. free from restraint; on a spree; ~ loose v/t untie, undo; release from confinement or constraint, set free; detatch; fire (gun); shoot (arrow); (eccles) absolve.
lose (p/t and p/part lost) [lOOz] v/t and i no longer have; be deprived of by accident or misfortune; mislay, fail to find; fail to get or win; be too late for; be bereaved of; waste; be defeated or beaten; suffer loss, become worse off; fail to hear, see or understand; cause or allow to perish; (of clock or watch) go too slowly; (refl) miss the right path; become absorbed in; l. one’s head become flustered, panic; l. one’s temper grow angry; l. one’s way fail to find the right path; l. out (US) be defeated after a struggle.
This knot is too loose. Please do not lose my book. I had better not lose that file.
One way to remember the difference between the two words is to think that “lose has lost an ‘o'”.