diff --git a/docs/index.md b/docs/index.md
index eeb44ea..03e59c9 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -25,4 +25,4 @@ and extending (`mrbgems`) mruby.
 ## Components
 
 - [API docs](api)
-- [mruby, mruby/c Common I/O API Guidance and Community-developed Libraries](https://github.com/mruby/microcontroller-peripheral-interface-guide)
+- [mruby, mruby/c Common I/O API Guideline and Community-developed Libraries](https://github.com/mruby/microcontroller-peripheral-interface-guide)