fortuitous

adjectives

having no cause or apparent cause
"a causeless miracle"; "fortuitous encounters--strange accidents of fortune"; "we cannot regard artistic invention as...uncaused and unrelated to the times"
causeless, fortuitous, uncaused
is derived from
fortuitousness
occurring by happy chance
"profits were enhanced by a fortuitous drop in the cost of raw materials"
fortuitous
is derived from
fortuitousness
is similar to
having unexpected good fortune
"other, less fortunate, children died"; "a fortunate choice"
fortunate