Defining Variables

1. String or Text:
   
   \def{\Message}{\textbf {Please always enjoy}}
   
   ...
   
   \Message, \Message an \Message.
   
2. A number (with TiKZ):
   
   \pgfmathparse{pi/4} \let\t\pgfmathresult;
\pgfmathparse{2*(1-cos(\t))} \let\ft\pgfmathresult;
   
3. List:
   
   \def\ns{1,2,4,7}
   
4. Points:
   
   \coordinate (P) at (4,5);