Invalid

Invalid may refer to:
 * Patient, a sick person
 * one who is confined to home or bed because of illness, disability or injury (sometimes considered a politically incorrect term)
 * .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