Define "source type" (singular)

index.html

@@ -245,7 +245,7 @@ <h3>Sampling and Reporting Rate</h3>
   <p>
     A <dfn>pressure source</dfn> is an abstract, [=implementation-defined=]
     interface to hardware counters or an underlying telemetry framework that
-    provides information about a <dfn>source types</dfn>
+    provides information about a <dfn>source type</dfn>
     defined by {{PressureSource}}. A [=pressure source=] can make use of data
     fusion with data from additional sources if that provides better results.
   </p>