> For the complete documentation index, see [llms.txt](https://ayakaleaf-pro.ayaka.space/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ayakaleaf-pro.ayaka.space/latex/zh-cn/latex-cuo-wu/14-latex-error-environment-xxx-undefined.md).

# LaTeX 错误：环境 XXX 未定义

如果你尝试使用一个 LaTeX 无法识别的环境，就会生成如下所示的错误信息：

main.tex，第5行

LaTeX 错误：环境 equation\* 未定义。

请参阅 LaTeX 手册或 LaTeX Companion 以获得说明。输入 H 可立即获得帮助。... l.5 \begin{equation\*} 你的命令已被忽略。输入 I 可用另一个命令替换它，或继续而不使用它。

## 常见原因

**你忘记加载某个宏包**

造成此错误的一个常见原因是，你正在尝试使用一个属于某个特定宏包的环境，但你忘记在导言区加载该宏包。一个例子就是 **`align`** 环境。 **`align`** 环境是 **`amsmath`** 宏包的一部分。因此，每当你使用 **`align`** 环境时，必须在导言区加入 **`\usepackage{amsmath}`** ，如下所示：

```latex
% 在导言区

\usepackage{amsmath}

% 在主 .tex 文件中

\begin{align}
2x + 3y &= 7\\
5x - 2y &= 2
\end{align}
```

![Align.PNG](/files/804dfcb28b681fece079c0a7e8ae90bebb39dfde)

如果你不在导言区包含 **`\usepackage{amsmath}`** ，就会生成一条错误信息。

**你把这个环境的拼写写错了：**

当环境的拼写本身是正确的时候，也会出现这种错误。下面展示了一个这样的错误示例：

```latex
\begin{lisQ}
    \item This is a list item
    \item This is another list item
\end{lisQ}
```

此处会出现错误，因为 **`list`** 环境被误写成了 **`lisQ`**。要修复这一点，只需在调用特定环境时检查拼写即可。

**不存在的环境**

此错误的另一种出现方式是，你试图使用一个不存在的环境。要了解 LaTeX 中允许使用的环境，以及如何创建自己的环境，请查看我们的 [文档](/latex/zh-cn/ming-ling/02-environments.md).


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