约化字

本书暂定概念：尚未进入正式概念库。下面是本书给出的定义原文。

定义 · 4.4 多面体的基本群

称为一个字，其中 $x_j\in X$ 且 $i_j\in \mathbb{Z}$。若 $i_j\ne 0$ 且 $x_j\ne x_{j+1}$，则称该字为约化字(reduced word)。任何字总可以经过有限步约化。例如，

$$a^{-2}{b}^{-3}{b}^3{a}^4{b}^3{c}^{-2}{c}^4=a^{-2}{b}^0{a}^4{b}^3{c}^2=a^2{b}^3{c}^2.$$

英文原文

is called a word, where $x_j\in X$ and $i_j\in \mathbb{Z}$ . If $i_j\ne 0$ and $x_j\ne x_{j+1}$ the word is called a reduced word. It is always possible to reduce a word by finite steps. For example,

$$a^{-2}{b}^{-3}{b}^3{a}^4{b}^3{c}^{-2}{c}^4=a^{-2}{b}^0{a}^4{b}^3{c}^2=a^2{b}^3{c}^2.$$

出处：4.4 多面体的基本群 · node a-359ca334ad2afffd2b1e6acd · 源节点 SHA-256 e700bbf92b0e4a74…