is just not shut below subtraction (that is definitely, subtracting 1 natural from A further would not often bring about An additional natural), means that N displaystyle mathbb N is actually a commutative monoid with identification aspect 0. It is just a free monoid on a single generator. This https://www.reddit.com/user/Similar-Taste2681/comments/1n7axgg/safe_herbal_supplements_for_daily_use_buy_from/