|warn vs worn||
Warn is a verb that means to inform someone in advance of an impending or possible danger, problem, or other unpleasant situation.
For example: I often warn people not to give out too much personal information on the net.
Worn is an adjective that is used to describe something affected by wear or damaged by long use. It is often paired with out as in worn-out which means damaged or shabby to the point being useless.
For example: He was wearing worn, shapeless shoes.
This headline from the BBC uses both words: Experts warn of 'epidemic' of worn-out heart valves.
!Note - Worn is also the past participle of to wear.