使框中的文字变为斜体

Question

我是 Latex 新手。我的问题是我想让框中的文本变成斜体。

\documentclass[a4paper,12pt,openany]{book}
\usepackage{etex}
\usepackage[utf8]{inputenc}
\usepackage{chngcntr}   
\usepackage{fontenc}
\usepackage[french]{babel}  
\usepackage{amsthm}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{color}
\usepackage{dsfont} 
\usepackage{lastpage} 
\usepackage{sectsty}
\usepackage[left=2cm,right=2cm,top=2.75cm,bottom=3cm]{geometry}
\usepackage[Bjornstrup]{fncychap}
\usepackage{hyperref}  
\usepackage[T1]{fontenc}
\usepackage{amssymb}
\usepackage[most]{tcolorbox}
\usepackage{cleveref}
\newtcbtheorem[auto counter, number within = section]{defn}{Définition}{
  colback=green!5,
  colframe=green!35!black,
  fonttitle=\bfseries,
}{t}
\begin{document}
\begin{defn}{}{}
asymptotically uniformly integrable relatively
\end{defn}
asymptotically uniformly integrable relatively
\end{document}

结果 ：

但是，我希望 Box 里面的文字形式如下：

Answer 1

欢迎光临！您在找什么fontupper=\itshape？

\documentclass[a4paper,12pt,openany]{book}
\usepackage[most]{tcolorbox}
\usepackage{cleveref}
\newtcbtheorem[auto counter, number within = section]{defn}{D\'efinition}{
  colback=green!5,
  colframe=green!35!black,
  fonttitle=\bfseries,
  fontupper=\itshape
}{t}
\begin{document}
\begin{defn}{}{}
asymptotically uniformly integrable relatively
\end{defn}
asymptotically uniformly integrable relatively
\end{document}