diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index a2b6fb85..6852bac6 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -481,7 +481,7 @@ battleship
   - [Subpackages](./packages/subpackages.md)
   - [Reverse Domain Name Notation](./packages/reverse_domain_name_notation.md)
 
-# Data Types IV
+# Data Types V
 
 - [Records](./records.md)
   - [Declaration](./records/declaration.md)
@@ -549,7 +549,7 @@ battleship
   - [Subtypes](./interfaces/subtypes.md)
   - [Multiple Implementations](./interfaces/multiple_implementations.md)
 
-# Data Types V
+# Data Types VI
 
 <!-- Note: Put a joke about the "A train leaves chicago at ..." problems.
 Make them do one. -->
@@ -621,7 +621,7 @@ Make them do one. -->
   - [Concurrent Modifications](./loops_iii/concurrent_modifications.md)
   - [Inferred Types](./loops_iii/inferred_types.md)
 
-# Concepts II
+# Concepts III
 
 - [Encapsulation](./encapsulation.md)
   - [Implementation Details](./encapsulation/implementation_details.md)
@@ -634,7 +634,7 @@ Make them do one. -->
   - [Information Hiding](./encapsulation/information_hiding.md)
 
 
-# Data Types VI
+# Data Types VII
 
 - [Collections](./collections.md)
   - [List](./collections/list.md)
@@ -714,7 +714,7 @@ Make them do one. -->
   - [Final Classes](./class_extension/final_classes.md)
 
 
-# Data Types VII
+# Data Types VIII
 
 - [Niche Numerics](./niche_numerics.md)
   - [byte](./niche_numerics/byte.md)
diff --git a/src/exceptions_ii/unchecked_exceptions.md b/src/exceptions_ii/unchecked_exceptions.md
index d2c64224..065cb886 100644
--- a/src/exceptions_ii/unchecked_exceptions.md
+++ b/src/exceptions_ii/unchecked_exceptions.md
@@ -1,6 +1,6 @@
 # Unchecked Exceptions
 
-When a part of your code might throw a "unchecked" exception, other
+When a part of your code might throw an "unchecked" exception, other
 parts of your code do not need to account for that possibility.
 
 ```java
diff --git a/src/interfaces.md b/src/interfaces.md
index 456e2230..624a03dd 100644
--- a/src/interfaces.md
+++ b/src/interfaces.md
@@ -2,7 +2,7 @@
 
 Generics let you write code that doesn't care
 what is different between different things - you would accept a `String`
-or an `Integer`, doesn't matter what is diferent between them.
+or an `Integer`, doesn't matter what is different between them.
 
 Interfaces do a related thing. They let you write code that takes advantage
 of commonalities.