diff --git a/reference/bc/book.xml b/reference/bc/book.xml
index 977f6063c2..b13a9c2a1d 100644
--- a/reference/bc/book.xml
+++ b/reference/bc/book.xml
@@ -19,7 +19,7 @@
     Passing values of type <type>float</type> to a BCMath function which expects
     a <type>string</type> as operand may not have the desired effect due to the
     way PHP converts <type>float</type> values to <type>string</type>, namely
-    that the <type>string</type> may be in exponential notation (what is not
+    that the <type>string</type> may be in exponential notation (which is not
     supported by BCMath), and that the decimal separator is locale dependend
     (while BCMath always expects a decimal point).
    </para>