in·va·lid·i·ty /ˌin-və-'li-də-tē/ n: lack of validity: state of being invalid

Merriam-Webster’s Dictionary of Law. . 1996.

I noun annulment, cancellation, disqualification, erroneousness, fallaciousness, fallacy, falseness, falsity, inadequacy, incompetence, ineffectiveness, nullity, unsoundness, untenableness, vitiation, voidness associated concepts: declaration of invalidity foreign phrases:
- Pacta quae turpem causam continent non sunt observanda. — Contracts which are based on an unlawful consideration will not be enforced.
- Pacta quae contra leges constitutionesque, vel contra bonos mores fiunt, nullam vim habere, indubitati juris est. — It is unquestionably the law that contracts which are made contrary to the laws or against good morals, have no force in law
- Quae ab initio non valent, ex post facto convalescere non possunt. — Things invalid from the beginning cannot be made valid by a subsequent act
II index disability (legal disqualification), disqualification (factor that disqualifies), impuissance, nullity

Burton's Legal Thesaurus. . 2006