diff --git a/src/gram.h b/src/gram.h
index 83dd8aac..3210b494 100644
--- a/src/gram.h
+++ b/src/gram.h
@@ -75,7 +75,7 @@
 
    RULES[R].line -- the line where R was defined.
 
-   RULES[R].useful -- true iff the rule is used (i.e., false if thrown
+   RULES[R].useful -- whether the rule is used (i.e., false if thrown
    away by reduce).
 
    The right hand side is stored as symbol numbers in a portion of
@@ -210,15 +210,15 @@ extern rule *rules;
 /* A function that selects a rule.  */
 typedef bool (*rule_filter) (rule const *);
 
-/* Return true IFF the rule has a 'number' smaller than NRULES.  That is, it is
-   useful in the grammar.  */
+/* Whether the rule has a 'number' smaller than NRULES.  That is, it
+   is useful in the grammar.  */
 bool rule_useful_in_grammar_p (rule const *r);
 
-/* Return true IFF the rule has a 'number' higher than NRULES.  That is, it is
+/* Whether the rule has a 'number' higher than NRULES.  That is, it is
    useless in the grammar.  */
 bool rule_useless_in_grammar_p (rule const *r);
 
-/* Return true IFF the rule is not flagged as useful but is useful in the
+/* Whether the rule is not flagged as useful but is useful in the
    grammar.  In other words, it was discarded because of conflicts.  */
 bool rule_useless_in_parser_p (rule const *r);
 
@@ -229,7 +229,7 @@ void rule_lhs_print (rule const *r, sym_content const *previous_lhs,
                      FILE *out);
 void rule_lhs_print_xml (rule const *r, FILE *out, int level);
 
-/* Return the length of the RHS.  */
+/* The length of the RHS.  */
 size_t rule_rhs_length (rule const *r);
 
 /* Print this rule's RHS on OUT.  */
@@ -252,7 +252,7 @@ extern int max_user_token_number;
 /* Dump RITEM for traces. */
 void ritem_print (FILE *out);
 
-/* Return the size of the longest rule RHS.  */
+/* The size of the longest rule RHS.  */
 size_t ritem_longest_rhs (void);
 
 /* Print the grammar's rules that match FILTER on OUT under TITLE.  */
diff --git a/src/reduce.c b/src/reduce.c
index 46eeebb5..f06cbf9b 100644
--- a/src/reduce.c
+++ b/src/reduce.c
@@ -39,13 +39,13 @@
 #include "reduce.h"
 #include "symtab.h"
 
-/* Set of all nonterminals whose language is not empty.  */
+/* Set of nonterminals whose language is not empty.  */
 static bitset N;
 
-/* Set of all rules which have no useless nonterminals in their RHS.  */
+/* Set of rules that have no useless nonterminals in their RHS.  */
 static bitset P;
 
-/* Set of all accessible symbols.  */
+/* Set of accessible symbols.  */
 static bitset V;
 
 /* Set of symbols used to define rule precedence (so they are
@@ -81,9 +81,11 @@ useful_production (rule_number r, bitset N0)
 }
 
 
-/*---------------------------------------------------------.
-| Remember that rules are 1-origin, symbols are 0-origin.  |
-`---------------------------------------------------------*/
+/*-----------------------------------------------------------------.
+| Compute N, the set of nonterminals whose language is not empty.  |
+|                                                                  |
+| Remember that rules are 1-origin, symbols are 0-origin.          |
+`-----------------------------------------------------------------*/
 
 static void
 useless_nonterminals (void)