diff --git a/doc/function/index.txt b/doc/function/index.txt
index 693c1fb4..c4eef234 100644
--- a/doc/function/index.txt
+++ b/doc/function/index.txt
@@ -29,7 +29,8 @@ These functions are built into the program, other [[type:function]]s can be defi
 	
 ! [[type:list|Lists]]		<<<
 | [[fun:position]]		Find the position of an element in a list.
-| [[fun:number_of_items]]	Find the number of items in a list.
+| [[fun:length]]		Return the number of items in a list.
+| [[fun:number_of_items]]	Return the number of items in a list.
 | [[fun:sort_list]]		Sort a list.
 | [[fun:filter_list]]		Filter a list, keeping only elements that match a predicate.
 	
diff --git a/doc/function/length.txt b/doc/function/length.txt
new file mode 100644
index 00000000..7798007b
--- /dev/null
+++ b/doc/function/length.txt
@@ -0,0 +1,22 @@
+Function: length
+
+--Usage--
+> length(some_collection)
+
+Returns the number of items in a list or the number of characters in a string.
+
+Note: This function is exactly the same as [[fun:number_of_items]].
+
+--Parameters--
+! Parameter	Type				Description
+| @input@	[[type:list]] or [[type:map]] or [[type:set]] or [[type:string]]
+		  				Object to determine the number of items of.
+		  				When it is a set, returns the number of cards.
+		  				When it is a string, returns the number of characters.
+
+--Examples--
+> length(["x", "y", "z"]) == 3
+> length("pink") == 4
+
+--See also--
+| [[fun:number_of_items]]	Return the number of items in a list.
diff --git a/doc/function/number_of_items.txt b/doc/function/number_of_items.txt
index 3c6014e7..727f4cd4 100644
--- a/doc/function/number_of_items.txt
+++ b/doc/function/number_of_items.txt
@@ -3,7 +3,9 @@ Function: number_of_items
 --Usage--
 > number_of_items(in: some_collection)
 
-Returns the position of an item in a list or characters in a string.
+Returns the number of items in a list or the number of characters in a string.
+
+Note: This function is exactly the same as [[fun:length]].
 
 --Parameters--
 ! Parameter	Type				Description
@@ -21,3 +23,8 @@ Returns the position of an item in a list or characters in a string.
 >
 > # the number of red cards in the set
 > number_of_items(in: set, filter: { card.color == "red" } )
+
+--See also--
+| [[fun:length]]	Return the number of items in a list.
+| [[fun:sort_list]]	Sort a list.
+| [[fun:filter_list]]	Filter a list, keeping only elements that match a predicate.
diff --git a/doc/function/position.txt b/doc/function/position.txt
index 70352c38..dae1aef0 100644
--- a/doc/function/position.txt
+++ b/doc/function/position.txt
@@ -24,3 +24,8 @@ If the item is not found in the list, returns @-1@.
 >
 > # The position of the card in the list of red cards, ordered by name
 > postion(of: card, in: set, order_by: {card.name}, filter:{card.color == "red"})
+
+--See also--
+| [[fun:length]] / [[fun:number_of_items]]	Return the number of items in a list.
+| [[fun:sort_list]]		Sort a list.
+| [[fun:filter_list]]		Filter a list, keeping only elements that match a predicate.