An indicator of the scientific status of a theory, in that it is in principle open to disproof. A good scientific hypothesis will make predictions about the world that expose it to refutation by empirical evidence.
See Falsifiability principle
The extent to which a particular theory can be tested and determined to be "false." Some critics of evolution believe that the evolution is not falsifiable.
Stating assertions in a way that permits them to be tested for truth or falsehood
The extent to which a scientific assertion is amenable to systematic probes, any one of which could negate the scientist's expectations.
In science and the philosophy of science, falsifiability, contingency, and defeasibility are roughly equivalent terms referring to the property of empirical statements that they must admit of logical counterexamples. This stands in contradistinction to formal and mathematical statements that may be tautologies, that is, universally true by dint of definitions, axioms, and proofs. Some philosophers and scientists, most notably Karl Popper, have asserted that no empirical hypothesis, proposition, or theory can be considered scientific if it does not admit the possibility of a contrary case.