Make LaTeX directly recognize unicode symbol [duplicate]

Question

I want to write the document in English, and copy-paste some text from online sources, where unicode symbols are usually used, for example:

$\frac{dω(τ)}{dτ}$

The letter tau is compilable in many places for example here, but not compliable on pdfLaTeX on Overleaf.

Is it possible to add a package to make things work?

Answer 1

If you want to (or must) stay with pdflatex, the package "alphabeta" (part of greek-fontenc) may help you:

\documentclass[]{article}
\usepackage{alphabeta}
\begin{document}
$\frac{dω(τ)}{dτ}$
\end{document}

Mind, that "alphabeta" and "unicode-math" are incompatible (the latter is to be preferred with Xe/LuaTeX).

Answer 2

In OpTeX, the Unicode Math is initialized when appropriate font family is selected by \fontfam. You needn't do more than:

\fontfam[lm]
$dω(τ)\over dτ$
\bye

Answer 3

Is it possible to add a package to make things work?

Such a package exists. Its name is unicode-math, and it's been around for several years already.

Observe that it's necessary to use either LuaLaTeX or XeLaTeX to process a document that loads the unicode-math package. To employ LuaLaTeX or XeLaTeX in Overleaf, I suggest you proceed as follows: In an Overleaf project, begin by opening the "Menu" drop-down list. Then, under the "Settings" header, open the "Compiler" box. The default compiler is pdfLaTeX; choose either LuaLaTeX or XeLaTeX and proceed from there.

%% compile with either LuaLaTeX or XeLaTeX
\documentclass{article}
\usepackage{unicode-math}
\begin{document}
$\frac{dω(τ)}{dτ}$
\end{document}