diff --git a/src/S31.xml b/src/S31.xml
index 71fb391b5..92681bb1b 100644
--- a/src/S31.xml
+++ b/src/S31.xml
@@ -125,7 +125,7 @@ or is your instructor guilty of a falsehood?</p>
 
 <p>As we will see when we discuss logical proofs, we can prove a conditional proposition by proving its contrapositive, which may be somewhat easier.</p>
 
-<p>Finally, there a third variation on the proposition <m>p \rightarrow q</m>, the inverse, which we will see that has the same logical meaning as the converse.</p>
+<p>Finally, there is a third variation on the proposition <m>p \rightarrow q</m>, the inverse, which we will see that has the same logical meaning as the converse.</p>
 
 <definition xml:id="def-inverse-proposition"><title>Logical Inverse</title>
 <idx><h>Inverse</h><h>Logical</h></idx>
@@ -267,4 +267,4 @@ For each of the following propositions, identify simple propositions, express th
 </exercise>
 
 </exercises>
-</section>
\ No newline at end of file
+</section>