diff --git a/ext/strscan/strscan.c b/ext/strscan/strscan.c
index 7eb6181203..42027cd8d2 100644
--- a/ext/strscan/strscan.c
+++ b/ext/strscan/strscan.c
@@ -981,7 +981,7 @@ strscan_unscan(VALUE self)
 }
 
 /*
- * Returns +true+ iff the scan pointer is at the beginning of the line.
+ * Returns +true+ if and only if the scan pointer is at the beginning of the line.
  *
  *   s = StringScanner.new("test\ntest\n")
  *   s.bol?           # => true
@@ -1034,7 +1034,7 @@ strscan_empty_p(VALUE self)
 }
 
 /*
- * Returns true iff there is more data in the string.  See #eos?.
+ * Returns true if and only if there is more data in the string.  See #eos?.
  * This method is obsolete; use #eos? instead.
  *
  *   s = StringScanner.new('test string')
@@ -1051,7 +1051,7 @@ strscan_rest_p(VALUE self)
 }
 
 /*
- * Returns +true+ iff the last match was successful.
+ * Returns +true+ if and only if the last match was successful.
  *
  *   s = StringScanner.new('test string')
  *   s.match?(/\w+/)     # => 4