A patent claim is indefinite if it fails to inform a person having ordinary skill in the art about the scope of the invention, with reasonable certainty. Reasonable certainty does not require absolute or mathematical precision. However case precedent has found patent claims to be indefinite when there is more than one way to measure a physical characteristic and the patent specification does not disclose how the inventor is measuring. The primary purpose of this requirement of definiteness of claim language is to ensure that the scope of the claims is clear so the public is informed of the boundaries of what constitutes infringement of the patent.