Apply suggestion using 'time' as example

Co-authored-by: Hans Olsson <HansOlsson@users.noreply.github.com>

chapters/operatorsandexpressions.tex

@@ -1536,4 +1536,6 @@ \subsection{Discrete-Time Expressions}\label{discrete-time-expressions}
 \subsection{Continuous-Time and Non-Discrete-Time Expressions}\label{continuous-time-expressions}
 
 All expressions are continuous-time expressions\index{continuous-time!expression}\index{expression variability!continuous-time} including constant, parameter and discrete-time expressions.
-The term \firstuse{non-discrete-time expression}\index{non-discrete-time expression}\index{expression variability!non-discrete-time} refers to expressions that are neither constant, parameter nor discrete-time expressions.  For example, a continuous-time variable (see \cref{component-variability-prefixes-discrete-parameter-constant}) is a non-discrete-time expression.
+The term \firstuse{non-discrete-time expression}\index{non-discrete-time expression}\index{expression variability!non-discrete-time} refers to expressions that are neither constant, parameter nor discrete-time expressions.  
+For example, \lstinline!time! is a continuous-time built-in variable (see \cref{component-variability-prefixes-discrete-parameter-constant}) and \lstinline!time+1! is a non-discrete-time expression.
+Note that plain \lstinline!time! may depending on context refer to the continuous-time variable or the non-discrete-time expression.