Update chapters/unitexpressions.tex

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/unitexpressions.tex

@@ -46,7 +46,7 @@ \section{The Syntax of Unit Expressions}\label{the-syntax-of-unit-expressions}
 \end{lstlisting}
 
 The SI standard uses super-script for the exponentation, and does thus not define any operator symbol for exponentiation.
-A \lstinline[language=grammar]!unit-factor! normally consists of a \lstinline[language=grammar]!unit-operand! possibly suffixed by a possibly signed integer number, which is interpreted as an exponent.
+A \lstinline[language=grammar]!unit-factor! consists of a \lstinline[language=grammar]!unit-operand! possibly suffixed by a possibly signed integer or rational number, which is interpreted as an exponent.
 Rational exponents are needed to fully support the unit for square roots (and can be used for roots in general).
 They are intended to be only be used when needed, i.e., not to represent integer exponents.
 There must be no spacing between the \lstinline[language=grammar]!unit-operand! and a possible \lstinline[language=grammar]!unit-exponent!.