is just not shut beneath subtraction (that may be, subtracting a single natural from A different doesn't generally bring about An additional natural), means that N displaystyle mathbb N This intuitive understanding (occasionally named selection perception), broadly has two distinctive but closely relevant aspects of what a natural variety https://share.evernote.com/note/b6ac86c4-49b5-8a83-fcdd-e9f84e4317c6