A defence to a case of infringement of an intellectual property right, in particular a patent, trademark or registered design. Invalidity with respect to patents can be found on a wide array of grounds including novelty (non-novelty), obviousness, misidentification of the inventor, fraud on the patent office (or very severe inequitable conduct), failure to teach the best-mode, failure to disclose the preferred embodiment, lack of enablement, indefiniteness, inoperability and failure to pay renewal fees. Trademarks are typically held invalid on relatively narrow grounds such as descriptiveness, genericization (genericide), naked licenses and assignments, non-use, indecency and failure to pay renewal fees. Designs, such as registered designs and design patents are typically argued to be invalid on grounds of functionality.