Uppercase word in glossary, lowercase in text

There is a simple solution. You can set the text that appears in the glossary and the text that appears in the... text separatly.

\newglossaryentry{uppercase}{
    name={Uppercase},
    text={uppercase},
    description={Appears uppercase in the glossary and lowercase in the text}
}

For future users encountering same trouble:

I ran into the problem myself and found this question and its duplicate. @Nitram's solution was useful in the case of a first word defined as a macro. However:

• I didn't want to duplicate all the name entries,
• I did want to keep control of what is capitalized and what isn't (case of mathematical symbols as first characters),
• I wanted to keep the usual behaviour if nothing is specifically asked.

From an answer by @nicola-talbot there, I found a simple redefinition that does the trick:

\usepackage{mfirstuc}
\renewcommand{\glsnamefont}[2][]{\capitalisewords{#1}\xspace#2}

Examples:

Usage: outputs "First word capitalized" in the glossary, and \gls{firstexample} in-text outputs "first word capitalized":

\newglossaryentry{firstexample}{
  name={first}{word capitalized}
}

This won't work with a macro (will capitalize whole word), hence use of text field:

\newglossaryentry{boite}{
  name={\Boite de valeurs},
  text={\boite de valeurs}
}

I have maths first, normal use of name: both in the glossary and in-text \gls{firstexample} output "$i$-th blabla":

\newglossaryentry{iblabla}{
  name={$i$-th blabla}
}

I've used Nicola's answer, since none of the answers here worked for me.

The glossaries-extra package allows to easily setup the capitalization with firstuc. I didn't had to change much of my previews code, nor calls. Just change the package and add the following code:

\setglossarystyle{long}
\setabbreviationstyle[acronym]{long-short}
\glssetcategoryattribute{acronym}{glossdesc}{firstuc}