Luck= (1) an unknown and unpredictable phenomenon that brings good fortune or adversity: We met each other out of pure luck. Bad luck caused his downfall.
Good fortune; be lucky, be in luck, (have) a stroke/bit of luck (NOT have luck): Were lucky the coach didn’t go without us. You’re in luck, there are still a few tickets left.
When luck is used with have, it is always modified: I’ve had enough bad luck to last me a lifetime.
Luck is an uncountable noun: He’s had a lot of bad luck recently. Meeting the right partner is just a matter of luck.