How to automate a dictionary (sorting, headers)?

Question

1. Here is a piece of solution to automate a dictionary using the links given in the first following comments.

   There are two problems to solve :

   • When one definition starts on one page and finishes on another, the words in the headinga are not the good ones. In my example below, take a look at the page 1 where the last word must be adhesive and not adhesion, and in the page 2, the first word must be adjacent and not adhesive. Is there a way to solve this problem ?
   • Secundly, I would like the letter A of the section to be centerd using \textbf{\textsf{...}} for formatting.

   Here is the code that I've wanted to improve.

   % Sources :
   %    1) http://tex.stackexchange.com/questions/30392/how-could-one-setup-a-layout-for-a-dictionary-if-possible
   %    2) http://tex.stackexchange.com/questions/26122/indexing-an-interval-of-words-on-top-of-every-page
   
   \documentclass[twoside]{article}
       \usepackage{multicol}
       \usepackage{ifthen}
       \usepackage{fancyhdr}
       \usepackage{enumerate}
       \usepackage{lipsum}
   
   % Empty \sectionmark
       \renewcommand{\sectionmark}[1]{}
   
       \fancyhead[L]{\textsf{\rightmark}}
       \fancyhead[R]{\textsf{\leftmark}}
       \fancyfoot[C]{\textbf{\textsf{\thepage}}}
   
   % Entry command : \dict{<word>}{<gender>}{<text>}
       \newcommand{\dict}[3]{%
           \par\vspace{0.25\baselineskip} %
           \textbf{\textsf{#1}} \textit{#2} #3 %
           \markboth{#1}{#1}
       }
   
       \pagestyle{fancy}
   
   
   \begin{document}
   
   \section*{A}
   
   \begin{multicols}{2}
       \dict{adequate}{n}{\lipsum[1]}
       \dict{adhere}{n}{\lipsum[2]}
       \dict{adherence}{n}{\lipsum[3]}
       \dict{adhesion}{n}{\lipsum[4]}
       \dict{adhesive}{n}{\lipsum[5]}
       \dict{adjacent}{n}{\lipsum[6]}
       \dict{adjective}{n}{\lipsum[1]}
       \dict{adjoin}{n}{\lipsum[2]}
       \dict{adjourn}{n}{\lipsum[3]}
       \dict{adjournment}{n}{\lipsum[4]}
       \dict{adjunt}{n}{\lipsum[5]}
       \dict{adjust}{n}{\lipsum[6]}
   \end{multicols}
   
   \end{document}
   

2. The solution found is the following one even if there is one remaining disturbing behavior, even if it is logical : in the last page of the output of the following code, zero appears in both headers...

   % Sources :
   %    1) http://tex.stackexchange.com/questions/30392/how-could-one-setup-a-layout-for-a-dictionary-if-possible
   %    2) http://tex.stackexchange.com/questions/26122/indexing-an-interval-of-words-on-top-of-every-page
   %    3) http://tex.stackexchange.com/questions/30947/how-to-automate-a-dictionary-sorting-headers/31017#31017
   
   \documentclass[twoside]{article}
       \usepackage{multicol}
       \usepackage{fancyhdr}
       \usepackage[bf,sf,center]{titlesec}
   
   % Headers and footers
       \fancyhead[L]{\textsf{\rightmark}}
       \fancyhead[R]{\textsf{\leftmark}}
   
       \fancyfoot[C]{\textbf{\textsf{\thepage}}}
   
       \renewcommand{\headrulewidth}{1.4pt}
       \renewcommand{\footrulewidth}{1.4pt}
   
   % Entry command : \dict{<word>}{<gender>}{<text>}
       \newcommand{\dict}[3]{%
           \markboth{#1}{#1}%
           \par\vspace{0.25\baselineskip}%
           \textbf{\textsf{#1}} \textit{- #2 -} #3%
       }
   
       \pagestyle{fancy}
   
   % For testing
       \usepackage{lipsum}
   
   
   \begin{document}
   
   \section*{A}
   
   \begin{multicols}{2}
       \dict{adequate}{n}{\lipsum[1]}
       \dict{adhere}{n}{\lipsum[2]}
       \dict{adherence}{n}{\lipsum[3]}
       \dict{adhesion}{n}{\lipsum[4]}
       \dict{adhesive}{n}{\lipsum[5]}
       \dict{adjacent}{n}{\lipsum[6]}
       \dict{adjective}{n}{\lipsum[1]}
       \dict{adjoin}{n}{\lipsum[2]}
       \dict{adjourn}{n}{\lipsum[3]}
       \dict{adjournment}{n}{\lipsum[4]}
       \dict{adjunt}{n}{\lipsum[5]}
       \dict{adjust}{n}{\lipsum[6]}
   \end{multicols}
   
   
   \section*{M}
   
   \begin{multicols}{2}
       \dict{main}{n}{\lipsum[3]}
       \dict{material}{n}{\lipsum[1]}
       \dict{mathematic}{n}{\lipsum[2]}
       \dict{more}{n}{\lipsum[2]}
   \end{multicols}
   
   
   \section*{Z}
   
   \begin{multicols}{2}
       \dict{zebra}{n}{\lipsum \lipsum \lipsum}
       \dict{zero}{n}{\lipsum[4]}
   \end{multicols}
   
   \end{document}
   

Answer 1

With regard to your first question (wrong header entries): In your \dict macro, use \markboth before typesetting the entry text.

\newcommand{\dict}[3]{%
  \markboth{#1}{#1}%
  \par\vspace{0.25\baselineskip}%
  \textbf{\textsf{#1}} \textit{#2} #3%
}

With regard to your second question (formatting the sectioning heading): Use, e.g.,

\usepackage[bf,sf,center]{titlesec}