diff --git a/packages/i18n/README.md b/packages/i18n/README.md
index 519a2ad6006c1b..d3206e55183cb7 100644
--- a/packages/i18n/README.md
+++ b/packages/i18n/README.md
@@ -38,8 +38,8 @@ _Related_
 
 _Parameters_
 
--   _data_ `?Object`: Locale data configuration.
--   _domain_ `?string`: Domain for which configuration applies.
+-   _data_ `[Object]`: Locale data configuration.
+-   _domain_ `[string]`: Domain for which configuration applies.
 
 <a name="sprintf" href="#sprintf">#</a> **sprintf**
 
@@ -73,7 +73,7 @@ _Parameters_
 -   _single_ `string`: The text to be used if the number is singular.
 -   _plural_ `string`: The text to be used if the number is plural.
 -   _number_ `number`: The number to compare against to use either the singular or plural form.
--   _domain_ `?string`: Domain to retrieve the translated text.
+-   _domain_ `[string]`: Domain to retrieve the translated text.
 
 _Returns_
 
@@ -94,7 +94,7 @@ _Parameters_
 -   _plural_ `string`: The text to be used if the number is plural.
 -   _number_ `number`: The number to compare against to use either the singular or plural form.
 -   _context_ `string`: Context information for the translators.
--   _domain_ `?string`: Domain to retrieve the translated text.
+-   _domain_ `[string]`: Domain to retrieve the translated text.
 
 _Returns_
 
@@ -112,7 +112,7 @@ _Parameters_
 
 -   _text_ `string`: Text to translate.
 -   _context_ `string`: Context information for the translators.
--   _domain_ `?string`: Domain to retrieve the translated text.
+-   _domain_ `[string]`: Domain to retrieve the translated text.
 
 _Returns_
 
@@ -129,7 +129,7 @@ _Related_
 _Parameters_
 
 -   _text_ `string`: Text to translate.
--   _domain_ `?string`: Domain to retrieve the translated text.
+-   _domain_ `[string]`: Domain to retrieve the translated text.
 
 _Returns_