规定了原点、正方向和单位长度的直线叫数轴。所有的实数都可以用数轴上的点来表示,也可以用数轴来比较两个实数的大小。一般取右方向为正方向,数轴上的点对应任意实数,包括无理数。数轴三要素:原点,单位长度,正方向。——摘自百度百科“数轴”词条 The line that defines the origin, positive direction, and unit length is called the number axis. All real numbers can be represented by points on the axis, and you can also use the axes to compare the sizes of two real numbers. In general, the right direction is taken as the positive direction, and the points on the axis correspond to any real number, including irrational numbers. Number axis three elements: origin, unit length, positive direction. - From Baidu Encyclopedia “number axis ” entry