Invalid may refer to:
- Patient, a sick person
- An archaic, politically incorrect term for a person with a disability
- .invalid, a top-level Internet domain not intended for real use
As the opposite of valid:
- Validity, in logic, true premises cannot lead to a false conclusion
- Validity (statistics), a measure which is measuring what it is supposed to measure
Famous quotes containing the word invalid:
“The invalid is a parasite on society. In a certain state it is indecent to go on living. To vegetate on in cowardly dependence on physicians and medicaments after the meaning of life, the right to life, has been lost ought to entail the profound contempt of society.”
—Friedrich Nietzsche (1844–1900)