# How can I typeset the reduced Planck constant (ℏ)? [duplicate]

How can I typeset the symbol for the reduced Planck constant (from quantum theory)? It consists in an italic "h" whose upper part is crossed by a small "slanted" bar:

For information, this slanted bar also occurs quite often with the letter "l" (ell) in Polish. Example: the Polish word for "word" is "slowo", where the letter "l" bears a slanted little bar.

Is there a package that provides that symbol?

Second question: please tell me where to look for and how to correct the LaTex PDF warning

overfull/underfull \hbox or \vbox


## marked as duplicate by egreg, jub0bs, Martin Schröder, Malipivo, JesseApr 12 '14 at 13:10

• Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. – user11232 Apr 12 '14 at 12:24
• I'm "tagging" the question so that it can be found by someone daring Unicode in a web search: the reduced Planck constant aka the Dirac constant is written ħ, pronounced as "h bar". – Christian Apr 12 '14 at 12:28
• To my knownledge, "reduced Planck constant" is the most widely accepted name for the physical constant you're referring to. Feel free to revert my edit if you don't like it. Also, you're asking two unrelated questions, here. Please ask only one question per post. That said, this should answer your question about bad boxes. – jub0bs Apr 12 '14 at 12:36

\documentclass{article}
$\hbar$ $\hslash$

\hbar needs no packages while \hslash needs amssymb.
Generally we prefer one question per thread. The badboxes are detailed in your .log file with line numbers. You may also add --file-line-error option to pdflatex to get C like error messages. Further, if you add draft option to the \documentclass[draft]{...}, the badboxes will be shown as black box in the pdf file. Good luck with it.