happening by chance

chance, random

happening unexpectedly

accidental, unforeseeable

not belonging (to what is being dealt with); coming from outside

unneeded; irrelevant

accompanying but not forming a necessary part; small and comparatively unimportant

related; minor

having, bringing, resulting from, good luck

fortunate, opportune

that can happen or be done, or may prove to be correct; that is reasonable or suitable

likely, attainable

without any particular reason

haphazard, chance