Natural This kind of function signifies a partial operate on naturals, exactly where the evidence of even (n) may be viewed as a precondition. From your Cambridge English Corpus There is not any serious distinction between the same old very first-order objects in the mathematical discourse - for instance naturals, https://medium.com/@cureayublog/cureayu-natural-healthcare-solutions-for-mind-body-balance-464977ee5d85?postPublishedType=initial