Small rewording

src/i_introduction/_5_Nullable_Types/NullableTypes.kt

@@ -55,7 +55,7 @@ fun fail() = throw Exception()
 fun todoTask5(client: Client?, message: String?, mailer: Mailer) = TODO(
     """
         Task 5.
-        Rewrite JavaCode5.sendMessageToClient in Kotlin, using only one 'if' statement.
+        Rewrite JavaCode5.sendMessageToClient in Kotlin, using only one 'if' expression.
         Declarations of Client, PersonalInfo and Mailer are given below.
     """,
     references = { JavaCode5().sendMessageToClient(client, message, mailer) }

src/i_introduction/_6_Smart_Casts/SmartCasts.kt

@@ -28,7 +28,7 @@ fun evalWhen(e: Expr): Int =
 fun todoTask6(expr: Expr) = TODO(
     """
         Task 6.
-        Rewrite 'JavaCode6.print()' in Kotlin using a 'when' statement.
+        Rewrite 'JavaCode6.print()' in Kotlin using a 'when' expression.
         Other examples of 'when' syntax can be found in the syntax/ifWhenExpressions.kt file.
     """,
     references = { JavaCode6().print(expr); syntax.ifWhenExpressions.whenWithoutArgument(42) })

src/syntax/javaCollections.kt

@@ -1,6 +1,6 @@
 package syntax.javaCollections
 
-// In Kotlin, Java standard collections are used, but there are two different manners of use:
+// In Kotlin, Java standard collections are used, but there are two representations of them:
 // mutable and read-only
 
 fun useReadonlySet(set: Set<Int>) {

src/v_collections/A_Introduction_.kt

@@ -10,7 +10,7 @@ import util.TODO
 
 /*
  *  For easy java compatibility we don't introduce our own collections, but use standard Java ones.
- *  However there are two different means of use: mutable and read-only.
+ *  However there are two representations of them: mutable and read-only.
  */
 
 fun useReadonlySet(set: Set<Int>) {

src/v_collections/B_FilterMap.kt

@@ -2,7 +2,7 @@ package v_collections
 
 fun example1(list: List<Int>) {
 
-    // If a lambda has exactly one argument, that agument can be accessed as 'it'
+    // If a lambda has exactly one parameter, that parameter can be accessed as 'it'
     val positiveNumbers = list.filter { it > 0 }
 
     val squares = list.map { it * it }