第一节整数的认识一自然数1.自然数的意义。自然数有几种解释:①用来表示物体个数的1、2、3……叫做自然数。这是用实例说明自然数。②非空有限的等价集合的标记叫做自然数。因为一类等价集合与其中任何一个集合的数量(即基数)是相同的,又因为一个集合的数量(即基数)实际就是集合的元素个数,所以也常 First, the realization of an integer a natural number 1. The meaning of natural numbers. There are several explanations of natural numbers: ① used to indicate the number of objects 1,2,3 ... ... called the natural number. This is an example of natural numbers. ② The non-empty finite set of equivalent labels is called natural number. Because a class of equivalent collection and any one of the collection of the same number (ie, base), and because a collection of the number (ie, cardinality) is actually the number of elements of the collection, it is often