Errors

LaTeX error messages can sometimes be tricky to understand and fix. We've put together a list of common errors below, along with more information about what they mean and how to solve them.

Alignment

• Misplaced alignment tab character &
• Extra alignment tab has been changed to \cr.

Double subscript

• Double subscript

Missing Math mode characters

• Display math should end with $$
• Missing $ inserted

References

• There were undefined references
• Reference XXX on page XXX undefined on input line XXX

Labeling

• There were multiply-defined labels.
• Label XXX multiply defined.

Float specifiers

• `!h' float specifier changed to `!ht'.
• `h' float specifier changed to `ht'."
• No positions in optional float specifier."

Undefined control sequences

• Undefined control sequence.

File not found

• File XXX not found on input line XXX."
• LaTeX Error: File XXX not found."
• Package pdftex.def Error: File XXX not found."

Missing number/illegal units of measure

• Missing number, treated as zero
• Illegal unit of measure (pt inserted)

Environment undefined (missing package)

• LaTeX Error: Environment tikzpicture undefined
• LaTeX Error: Environment theorem undefined
• LaTeX Error: Environment split undefined
• LaTeX Error: Environment minipage* undefined
• LaTeX Error: Environment maplelatex undefined
• LaTeX Error: Environment mapleinput undefined
• LaTeX Error: Environment maplegroup undefined
• LaTeX Error: Environment flalign undefined
• LaTeX Error: Environment figure* undefined
• LaTeX Error: Environment comment undefined
• LaTeX Error: Environment biblio_lat undefined
• LaTeX Error: Environment align* undefined
• LaTeX Error: Environment align undefined
• LaTeX Error: Environment algorithm undefined
• LaTeX Error: Environment adjustbox undefined

Underfull and overfull boxes

Although these warnings are not errors we list them here for convenience:

• Understanding underfull and overfull box warning

Other

• LaTeX Error: Can be used only in preamble
• LaTeX Error: Missing \begindocument
• LaTeX Error: \verb ended by end of line
• No \author given
• Misplaced \noalign
• LaTeX Error: Something's wrong--perhaps a missing \item
• There's no line here to end
• Unknown graphics extension: .XXX