> For the complete documentation index, see [llms.txt](https://overleaf-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://overleaf-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 LaTeX 无法识别的环境，你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 以获取解释。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 可将其替换为另一个命令，或者继续而不使用它。

## 常见原因

**你忘记加载某个宏包**

这种错误的常见原因是，你正在尝试使用某个特定宏包的一部分环境，但你忘记在导言区加载该宏包。一个例子是 **`align`** 环境。 **`align`** 该环境是 **`amsmath`** 宏包的一部分。因此，每当你使用 **`align`** 环境时，你必须在导言区包含 **`\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)

如果你不包含 **`\usepackage{amsmath}`** 在导言区，你将生成一条错误信息。

**你把该环境拼写错了：**

另一个这种错误的常见例子是，当环境被正确拼写时。下面展示了这种错误的一个示例：

```latex
\begin{lisQ}
    \item 这是一个列表项
    \item 这是另一个列表项
\end{lisQ}
```

这里会出现一个错误，因为 **`list`** 环境被误写成了 **`lisQ`**。要修复此问题，只需在调用特定环境时检查拼写。

**环境不存在**

这种错误出现的另一种情况是，你尝试使用一个不存在的环境。要了解更多关于 LaTeX 中允许使用的环境，以及如何创建你自己的环境，请查看我们的 [文档](/latex/zh-cn/ming-ling/02-environments.md).


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