符号的英文表达

+ plus  加；正
- minus  减；负
± plus-minus  正负
* is multiplied by / multipication sign  乘
÷ is divided by / division sign  除
= is equal to  等于
≠ is not equal to  不等于
≡ or === is equivalent to  全等于/恒等于
? is approximately equal to or equal to / almost equal or equal to  等于或约等于
≈ is approximately equal to / almost equal to  约等于
< is less than  小于
> is greater than  大于
≮ is not less than  不小于
≯ is not greater than  不大于
≤ is less than or equal to  小于或等于
≥ is greater than or equal to  大于或等于
% percent / per cent  百分之…
‰ per mille  千分之…
? per ten thousand  万分之…
∞ infinity  
∝ varies as / proportional to 与...成比例
√ square root  平凡根
? cube root
∴ hence / therefor  所以 
∵ since / because  因为
∶ ratio  比率；比例
∷ equals / proportion  成比例
∠ angle  角
⌒ semicircle  半圆
⊙ circle 圆
○ circumference  圆周
△ 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
＃ number …号
℃ Celsius system 摄氏度
＠ at 在

参考：
51Talk无忧英语 / Mac简体拼音输入法