Invalidity (noun)

1. The state or quality of being invalid, especially the state of being legally or logically null and void.
2. The state of being weak, disabled, or unfit, especially physically or mentally.

Origin:

Late latin invaliditas, from latin invalidus weak, from in- not + validus strong.

Examples:

1. The invalidity of the contract was proven by evidence of fraud and misrepresentation.
2. The invalidity of the will was challenged on the grounds of undue influence.
3. The invalidity of the election results was proven by systematic voter suppression and fraud.
4. The invalidity of the argument was demonstrated by the lack of evidence and logical fallacies.
5. The invalidity of the patent was established by prior art and prior use.