A "fact" can be defined as something that is the case—that is, a state of affairs.
Facts may also be understood as those things to which a true sentence refers.
For example, "If Alexander had lived, his empire would have been greater than Rome." This contrasts with an indicative conditional, which indicates what is (in fact) the case if its antecedent is (in fact) true—for example, "If you drink this, it will make you well." Such sentences are important to modal logic, especially since the development of possible world semantics.
In science, a fact is a repeatable careful observation or measurement (by experimentation or other means), also called empirical evidence. Various forms of observation and measurement lead to fundamental questions about the scientific method, and the scope and validity of scientific reasoning.
The statement "Jupiter is the largest planet in the solar system" is about the fact Jupiter is the largest planet in the solar system.
This theory presupposes the existence of an objective world.
Factuality—what has occurred—can also be contrasted with counterfactuality: what might have occurred, but did not.