(Granted, that's not always the case, but we're trying to keep it simple.)
Tip: If you're unsure about which spelling to use, put your sentence in past tense; if "lost" is the verb you end up with, then "lose" is the spelling you want.
Loose, from Dictionary.com:
[loos]
–adjective
1.
free or released from fastening or attachment: a loose end.
2.
free from anything that binds or restrains; unfettered: loose cats prowling around in alleyways at night.
3.
uncombined, as a chemical element.
4.
not bound together: to wear one's hair loose.
5.
not put up in a package or other container: loose mushrooms.
6.
available for disposal; unused; unappropriated: loose funds.
7.
lacking in reticence or power of restraint: a loose tongue.
8.
lax, as the bowels.
9.
lacking moral restraint or integrity; notorious for his loose character.
10.
sexually promiscuous or immoral; unchaste.
11.
not firm, taut, or rigid: a loose tooth; a loose rein.
12.
relaxed or limber in nature: He runs with a loose, open stride.
13.
not fitting closely or tightly: a loose sweater.
14.
not close or compact in structure or arrangement; having spaces between the parts; open: a loose weave.
15.
having few restraining factors between associated constituents and allowing ample freedom for independent action: a loose federation of city-states.
16.
not cohering: loose sand.
17.
not strict, exact, or precise: a loose interpretation of the law.
18.
Sports .
a.
having the players on a team positioned at fairly wide intervals, as in a football formation.
b.
(of a ball, hockey puck, etc.) not in the possession of either team; out of player control.
–adverb
19.
in a loose manner; loosely (usually used in combination): loose-flowing.
–verb (used with object)
20.
to let loose; free from bonds or restraint.
21.
to release, as from constraint, obligation, or penalty.
22.
Chiefly Nautical . to set free from fastening or attachment: to loose a boat from its moorings.
23.
to unfasten, undo, or untie, as a bond, fetter, or knot.
24.
to shoot; discharge; let fly: to loose missiles at the invaders.
25.
to make less tight; slacken or relax.
26.
to render less firmly fixed; lessen an attachment; loosen.
–verb (used without object)
27.
to let go a hold.
28.
to hoist anchor; get under way.
29.
to shoot or let fly an arrow, bullet, etc. (often fol. by off ): to loose off at a flock of ducks.
30.
Obsolete . to become loose; loosen.
—Idioms
31.
break loose, to free oneself; escape: The convicts broke loose.
32.
cast loose,
a.
to loosen or unfasten, as a ship from a mooring.
b.
to send forth; set adrift or free: He was cast loose at an early age to make his own way in the world.
33.
cut loose,
a.
to release from domination or control.
b.
to become free, independent, etc.
c.
to revel without restraint: After the rodeo they headed into town to cut loose.
34.
hang / stayloose, Slang . to remain relaxed and unperturbed.
35.
let loose,
a.
to free or become free.
b.
to yield; give way: The guardrail let loose and we very nearly plunged over the edge.
36.
on the loose,
a.
free; unconfined, as, esp., an escaped convict or circus animal.
b.
behaving in an unrestrained or dissolute way: a bachelor on the loose.
37.
turn loose, to release or free, as from confinement: The teacher turned the children loose after the class.
Lose, from Dictionary.com:
[looz] verb, lost, los·ing.
–verb (used with object)
1.
to come to be without (something in one's possession or care), through accident, theft, etc., so that there is little or no prospect of recovery: I'm sure I've merely misplaced my hat, not lost it.
2.
to fail inadvertently to retain (something) in such a way that it cannot be immediately recovered: I just lost a dime under this sofa.
3.
to suffer the deprivation of: to lose one's job; to lose one's life.
4.
to be bereaved of by death: to lose a sister.
5.
to fail to keep, preserve, or maintain: to lose one's balance; to lose one's figure.
6.
(of a clock or watch) to run slower by: The watch loses three minutes a day.
7.
to give up; forfeit the possession of: to lose a fortune at the gaming table.
8.
to get rid of: to lose one's fear of the dark; to lose weight.
9.
to bring to destruction or ruin (usually used passively): Ship and crew were lost.
10.
to condemn to hell; damn.
11.
to have slip from sight, hearing, attention, etc.: to lose him in the crowd.
12.
to stray from or become ignorant of (one's way, directions, etc.): to lose one's bearings.
13.
to leave far behind in a pursuit, race, etc.; outstrip: She managed to lose the other runners on the final lap of the race.
14.
to use to no purpose; waste: to lose time in waiting.
15.
to fail to have, get, catch, etc.; miss: to lose a bargain.
16.
to fail to win (a prize, stake, etc.): to lose a bet.
17.
to be defeated in (a game, lawsuit, battle, etc.): He has lost very few cases in his career as a lawyer.
18.
to cause the loss of: The delay lost the battle for them.
19.
to let (oneself) go astray, miss the way, etc.: We lost ourselves in the woods.
20.
to allow (oneself) to become absorbed or engrossed in something and oblivious to all else: I had lost myself in thought.
21.
(of a physician) to fail to preserve the life of (a patient).
22.
(of a woman) to fail to be delivered of (a live baby) because of miscarriage, complications in childbirth, etc.
–verb (used without object)
23.
to suffer loss: to lose on a contract.
24.
to suffer defeat or fail to win, as in a contest, race, or game: We played well, but we lost.
25.
to depreciate in effectiveness or in some other essential quality: a classic that loses in translation.
26.
(of a clock, watch, etc.) to run slow.
—Verb phrase
27.
lose out, to suffer defeat or loss; fail to obtain something desired: He got through the preliminaries, but lost out in the finals.
—Idiom
28.
lose face. face ( def. 48 ) .