你这个是正负号,plus or minus three
下面是常用数学符号的英语对照:
+ plus 加号；正号
- minus 减号；负号
± plus or minus 正负号
× is multiplied by 乘号
÷ is divided by 除号
＝ is equal to 等于号
≠ is not equal to 不等于号
≡ is equivalent to 全等于号
≌ is equal to or approximately equal to 等于或约等于号
≈ is approximately equal to 约等于号
＜ is less than 小于号
＞ is more than 大于号
≮ is not less than 不小于号
≯ is not more than 不大于号
≤ is less than or equal to 小于或等于号
≥ is more than or equal to 大于或等于号
% per cent 百分之...
‰ per mill 千分之...
∞ infinity 无限大号
∝ varies as 与...成比例
√ (square) root 平方根
∵ since; because 因为
∴ hence 所以
∷ equals,as (proportion) 等于,成比例
∠ angle 角
⌒ semicircle 半圆
⊙ circle 圆
○ circumference 圆周
π pi 圆周率
△ triangle 三角形
⊥ perpendicular to 垂直于
∪ union of 并,合集
∩ intersection of 交,通集
∫ the integral of ...的积分
∑ (sigma) summation of 总和
° degree 度
′ minute 分
〃 second 秒
℃ Celsius system 摄氏度