The spelling of loose and lose is similar, but the meaning is different:
My tooth is loose. I’m afraid I might lose it.
Rather than provide definitions (which can be found easily) I’ll give examples of how these two words are often used. Repetition aids memory!
“I think he’s got a screw loose.”
“I prefer loose-fitting clothing in hot weather.”
The escaped convicts are on the loose.
“Hang loose, man!”
“But Jeb told me to loose the horses!”
“In my day, we’d have called her a loose woman.”
“With a wave of this wand, I loose the demons that are trapped beneath the waves!”
Loosen your grip on the steering wheel and enjoy the ride!
“I must loosen my belt after that meal!”
“I don’t want to lose you.”
“My career may be over if I lose this race.”
Lose the e when spelling losing.
Lost is the past tense of lose; loosed is the past tense of loose.
Sally lost ten pounds through diet and exercise.
Joe lost his temper and destroyed the model Jeri had built.
When Zeus loosed his fury, the ground shook.
Lost can also be an adjective: The lost child wailed.
The use of lost cause (a noun) arose after the defeat of the Confederacy.
And remember: “Don’t be a sore loser!”