prob·a·bil·i·ty

– noun
1. the quality or fact of being probable.
2. a strong likelihood or chance of something.
3. a probable event, circumstance, etc.
4. a. the relative possibility that an event will occur, as expressed by the ratio of the number of actual occurrences to the total number of possible occurrences.
b. the relative frequency with which an event occurs or is likely to occur.

ra·tio

– noun
1. the relation between two similar magnitudes with respect to the number of times the first contains the second.
2. proportional relation; rate.