diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 0b9b1fb..52aa41c 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -220,7 +220,7 @@
 The grammar for a replacement field is as follows:
 
    .. productionlist:: sf
-      replacement_field: "{" `field_name` ["!" `conversion`] [":" `format_spec`] "}"
+      replacement_field: "{" [`field_name`] ["!" `conversion`] [":" `format_spec`] "}"
       field_name: arg_name ("." `attribute_name` | "[" `element_index` "]")*
       arg_name: (`identifier` | `integer`)?
       attribute_name: `identifier`
@@ -228,7 +228,7 @@
       conversion: "r" | "s"
       format_spec: <described in the next section>
 
-In less formal terms, the replacement field starts with a *field_name* that specifies
+In less formal terms, the replacement field can start with a *field_name* that specifies
 the object whose value is to be formatted and inserted
 into the output instead of the replacement field.
 The *field_name* is optionally followed by a  *conversion* field, which is
@@ -249,7 +249,7 @@
 
    "First, thou shalt count to {0}" # References first positional argument
    "Bring me a {}"                  # Implicitly references the first positional argument
-   "From {} to {}"                  # Same as "From {0] to {1}"
+   "From {} to {}"                  # Same as "From {0} to {1}"
    "My quest is {name}"             # References keyword argument 'name'
    "Weight in tons {0.weight}"      # 'weight' attribute of first positional arg
    "Units destroyed: {players[0]}"  # First element of keyword argument 'players'.