Unique because it has a pattern of the mathematical symbol pi.

之所以说它特别是因为上面有圆周率π的数学符号。

For starters, X wasn't even a letter a few thousand years ago, let alone a mathematical symbol.

首先，几千年前，X 甚至不是一个字母，更不用说数学符号了。

Penny's clothing is unusual because it has images in the shape of the mathematical symbol pi.

Penny 的衣服很不寻常， 因为它有数学符号 pi 形状的图像。

When written using mathematical symbols, the differences are obvious because " for all" and " there exists" are reversed.

当用数学符号书写时，差异是明显的，因为" 所有" 和" 存在" 是相反的。

Unfortunately the rules are more difficult to follow when the language of discourse is English instead of mathematical symbols.

不幸的是，当话语语言是英语而不是数学符号时，规则就更难遵循了。

There are terms like convexity and duration and there are mathematical symbols, but people don't really use those very much on a day-to-day basis.

其中有凸度、持续时间等术语以及数学符号，但人们在日常生活中并不经常使用它们。

The " number pad" is a small, usually square or rectangular part of a keyboard that has just numbers as well as a few mathematical symbols.

“数字键盘” 是键盘上一个很小的部分，通常是正方形或长方形， 只有数字和一些数学符号。