Why can't I show the ð symbol in LaTeX?

Question

I can use \DeclareUnicodeCharacter{0278}{\phi} and then $ɸ$ to display the ɸ symbol in LaTeX. However, when I try to use:

\usepackage[utf8]{inputenc}

\DeclareUnicodeCharacter{0360}{\eth}

\begin{document}

$ð$

\end{document}

ð doesn't display. Why doesn't this work?

Answer 1

You need

• a package which provides the \eth macro in the encoding you are using, e.g. stix
• the \eth macro from this package is, unlike \phi, a text macro and not a math macro, so either use it outside of a math environment or surround it with \text{..} from the amsmath package
• if your tex distribution is not totally out of date, you don't need \usepackage[utf8]{inputenc}, that's the default since a couple of years

---

\documentclass{article}

\usepackage{amsmath}
\usepackage{stix}
\DeclareUnicodeCharacter{0360}{\eth}

\begin{document}

ð

$\text{ð}$

\end{document}

or avoid all the trouble and simply use an unicode aware engine like lualatex:

% !TeX TS-program = lualatex
\documentclass{article}

\begin{document}

ð

\end{document}