Add a description of what is an errata

Signed-off-by: Aurélien Bouteiller <[email protected]>

Author: abouteiller

Chap_Terms.tex

@@ -128,6 +128,7 @@ \section{Semantics}
 \begin{itemize}
 \item \emph{shall}, \emph{must} and \emph{will} indicate that the specified behavior is \emph{required} of all conforming implementations
 \item \emph{should} and \emph{may} indicate behaviors that a complete implementation would include, but are not required of all conforming implementations
+\item \emph{errata} indicate a clarification or minor correction to the standard (that is, backward compatible, or representing the state of the practice in implementations); such changes to an API or attribute apply retroactively to all prior versions of the standard where said API or attribute exists
 \end{itemize}
 
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