Paragraph ended before \foo was complete / Runaway argument?

TeX Output

Runaway argument?
{First line. 
./example.tex:5: Paragraph ended before \textbf was complete.
<to be read again> 
                   \par 
l.5 

Explanation

In TeX, macros are by default “short” (not \long), meaning their arguments cannot contain paragraph breaks (\par or blank lines). This error typically happens when:

1. An opening brace { after a macro like \textbf{, \section{, or \emph{ was never closed, and the compiler hit a blank line.
2. An intended multi-paragraph block was passed into a single-paragraph formatting macro.

How to Fix

• Close the unclosed brace { on the line where the macro was opened.
• If multiple paragraphs need formatting, format each paragraph separately, or use an environment (e.g. \begin{quote} ... \end{quote}) or switch commands ({\bfseries ... \par ...}).