chance

a possibility due to a favorable combination of circumstances

the holiday gave us the opportunity to visit Washington

an unknown and unpredictable phenomenon that causes an event to result one way rather than another

bad luck caused his downfall

a risk involving danger

you take a chance when you let her drive

a measure of how likely it is that some event will occur; a number expressing the ratio of favorable cases to the whole number of cases possible

the probability that an unbiased coin will fall with the head up is 0.5

the possibility of future success

his prospects as a writer are excellent

occurring or appearing or singled out by chance

seek help from casual passers by

be the case by chance

I chanced to meet my old friend in the street