 Mandatory status is defended by listing paradigm cases of ‘borderline’. Just as a language teacher tests for competence by having students distinguish clear positive from clear negatives, she also tests by their recognition of borderline cases. Any pupil who uses ‘-ish’ without recognizing borderline cases of ‘noonish’ has not yet mastered the suffix. ‘Noonish’ is not a synonym of ‘within ten minutes of noon’ or any other term with a precisely delimited interval.