probability

n. likelihood, reasonability, odds; chance, prospect, outlook

Probability is the likelihood that something is the case or will happen. Probability theory is used extensively in areas such as statistics, mathematics, science and philosophy to draw conclusions about the likelihood of potential events and the underlying mechanics of complex systems.
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Noun
1. a measure of how likely it is that some event will occur; "what is the probability of rain?"; "we have a good chance of winning"
(synonym) chance
(hypernym) measure, quantity, amount
(hyponym) conditional probability, contingent probability
2. the quality of being probable
(antonym) improbability, improbableness
(hypernym) quality
(hyponym) likelihood, likeliness, odds

(n.)
The quality or state of being probable; appearance of reality or truth; reasonable ground of presumption; likelihood.
  

(n.)
That which is or appears probable; anything that has the appearance of reality or truth.
  

(n.)
Likelihood of the occurrence of any event in the doctrine of chances, or the ratio of the number of favorable chances to the whole number of chances, favorable and unfavorable. See 1st Chance, n., 5.
  

Medicine is to a significant degree based on probability theory. Probability in this context is the likelihood of something happening. The abbreviation for probability is P. For example, P<0.05 indicates that the probability of something occurring by chance alone is less than 5 in 100, or 5%. As a matter of fact, P<0.05 is usually taken as the level of biologic significance where a result may be considered meaningful.