
Probability
Probability is a measure quantifying the likelihood that events will occur. See glossary of probability and statistics. Probability quantifies as a number between 0 and 1, where, loosely speaking, 0 indicates impossibility and 1 indicates certainty. The higher the probability of an event, the more likely it is that the event will occur. A simple example is the tossing of a fair (unbiased) coin. Since the coin is fair, the two outcomes (“heads” and “tails”) are both equally probable; the probability of “heads” equals the probability of “tails”; and since no other outcomes are possible, the probability of either “heads” or “tails” is 1/2 (which could also be written as 0.5 or 50%).
These concepts have been given an axiomatic mathematical formalization in probability theory, which is used widely in such areas of study as mathematics, statistics, finance, gambling, science (in particular physics), artificial intelligence/machine learning, computer science, game theory, and philosophy to, for example, draw inferences about the expected frequency of events. Probability theory is also used to describe the underlying mechanics and regularities of complex systems.

Possibility (noun)
The quality of being possible.

Possibility (noun)
A thing possible; that which may take place or come into being.

Possibility (noun)
An option or choice, usually used in context with future events.

Probability (noun)
The state of being probable; likelihood.

Probability (noun)
An event that is likely to occur.

Probability (noun)
The relative likelihood of an event happening.

Probability (noun)
A number, between 0 and 1, expressing the precise likelihood of an event happening.
“The probability of an event A occurring is denoted P(A).”

Possibility (noun)
a thing that may happen or be the case
“there was the possibility that he might be turned down”
“relegation remains a distinct possibility”

Possibility (noun)
the state or fact of being possible; likelihood
“there is no possibility of any government achieving this level of expenditure”

Possibility (noun)
a thing that may be chosen or done out of several possible alternatives
“one possibility is to allow all firms to participate”

Possibility (noun)
unspecified qualities of a promising nature; potential
“the house was old but it had possibilities”

Probability (noun)
the quality or state of being probable; the extent to which something is likely to happen or be the case
“the rain will make the probability of a postponement even greater”

Probability (noun)
a probable or the most probable event
“for a time revolution was a strong probability”

Probability (noun)
the extent to which an event is likely to occur, measured by the ratio of the favourable cases to the whole number of cases possible
“a probability of 0.5”
“the area under the curve represents probability”