diff --git a/docs/TypeChecker.rst b/docs/TypeChecker.rst
index 5b680040ec842..a1e1e8bc885a1 100644
--- a/docs/TypeChecker.rst
+++ b/docs/TypeChecker.rst
@@ -486,7 +486,7 @@ down to only simple constraints that are trivially satisfied.
 The simplification process breaks down constraints into simpler
 constraints, and each different kind of constraint is handled by
 different rules based on the Swift type system. The constraints fall
-intofive categories: relational constraints, member constraints,
+into five categories: relational constraints, member constraints,
 type properties, conjunctions, and disjunctions. Only the first three
 kinds of constraints have interesting simplification rules, and are
 discussed in the following sections.