diff --git a/doc/lua_api.md b/doc/lua_api.md
index ab8efd411..d58ed5fc2 100644
--- a/doc/lua_api.md
+++ b/doc/lua_api.md
@@ -2026,6 +2026,17 @@ that acts as tool in a gameplay sense as a craftitem, and vice-versa.
 Craftitems can be used for items that neither need to be a node
 nor a tool.
 
+Special Items
+-------------
+The following items are predefined and have special properties.
+
+* `"unknown"`: An item that represents every item which has not been registered
+* `"air"`: The node which appears everywhere where no other node is
+* `"ignore"`: Mapblocks which have not been yet generated consist of this node
+* `""`: The player's hand, which is in use whenever the player wields no item
+  * Its rage and tool capabilities are also used as an fallback for the wield item
+  * It can be overridden to change those properties
+
 Amount and wear
 ---------------