> 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/latex-errors/30-there-were-undefined-references.md).

# There were undefined references

This error appears when **`\ref{...}`** is used and LaTeX is unable to find the corresponding label. There are three ways in which this can happen.

* There is a typo in **`\label{...}`**
* There is a typo in **`\ref{...}`**
* A label has been forgotten.

An example is shown below

```latex
\section{introduction}\label{introduction}
A typo when referencing the introduction would be \ref{intorduction}.

Another error is referencing a label which has never been defined such as \ref{section1}
```

Each of these will generate an error which looks like

main.tex, line 6

Reference \`intorduction' on page 1 undefined on input line 6.

main.tex, line 6

Reference \`section1' on page 1 undefined on input line 8.

main.tex, line 6

There were undefined references.

To avoid this, we must always make sure that when we use **`\ref{...}`**, that there is a corresponding **`\label{...}`**, and that the arguments of **`\ref{...}`** and **`\label{...}`** are the same.


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