an unknown and unpredictable phenomenon that causes an event to result one way rather than another; "bad luck caused his downfall"; "we ran into each other by pure chance"
an unknown and unpredictable phenomenon that leads to a favorable outcome; "it was my good luck to be there"; "they say luck is a lady"; "it was as if fortune guided his hand"
experiencing or marked by or causing sadness or sorrow or discontent; "unhappy over her departure"; "unhappy with her raise"; "after the argument they lapsed into an unhappy silence"; "had an unhappy time at school"; "the unhappy (or sad) news"; "he looks so sad"