> 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-tw/latex-cuo-wu/13-latex-error-can-be-used-only-in-preamble.md).

# LaTeX 錯誤：只能在前言中使用

當你把套件或類別包含在文件的主體中，而不是放在前言區時，就會出現這個錯誤。文件的前言區包含在之前寫下的所有內容 **`\begin{document}`**。在前言區中，你定義正在撰寫的文件類型、語言以及其他幾個元素。例如，一個正常的文件前言區會像這樣：

```latex
\documentclass[12pt, letterpaper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\title{First document}
\author{Hubert Farnsworth \thanks{funded by the ShareLaTeX team}}
\date{February 2014}
```

如果你寫入 **`\usepackage{...}`** 在文件的主體中（在 **`\begin{document}`**）之後，而不是放在前言區，你就會產生如下所示的錯誤訊息。

main.tex，第 7 行

LaTeX 錯誤：只能在前言區中使用。

請參閱 LaTeX 手冊或 LaTeX Companion 以了解說明。輸入 H 取得即時說明。... l.4 \usepackage {amsmath} 你的命令已被忽略。輸入 I 以將其替換為另一個命令，或在不使用它的情況下繼續。\[1

要修正這個錯誤，請確認所有 **`\usepackage{...}`** 命令，以及 **`\documentclass[...]{...}`**，都寫在 **`\begin{document}`**之前。若要進一步了解如何在 LaTeX 中結構化文件，請查看我們的 [說明文件](/latex/zh-tw/latex-ji-chu/01-learn-latex-in-30-minutes.md).


---

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