diff --git a/Algo/CM/CM du 27 septembre.md b/Algo/CM/CM du 27 septembre.md
index 9741727..892d6e7 100644
--- a/Algo/CM/CM du 27 septembre.md	
+++ b/Algo/CM/CM du 27 septembre.md	
@@ -37,13 +37,15 @@
 					- `not_: boolean -> boolean`
 					- `_and_: boolean x boolean -> boolean`
 					- `_or_: boolean x boolean -> boolean`
-			- Vectors
-				- Uses: integer and element
+			- Vectors (defined type)
+				- Uses: integer and element (predefined types)
 				- Operations:
-					- `modify: vector x integer x element -> vector`
+					- `modify: vector x integer x element -> vector` (internal operation)
 					- `nth: vector x integer -> element`
-					- `lowerlimit: vector -> integer`
+					- `lowerlimit: vector -> integer` (observers)
 					- `upperlimit: vector -> integer`
 				- Use
 					- `nth(v, i+2)`
-					- 
\ No newline at end of file
+> Every time that an operation return a defined type, is a **internal operation.**
+> **An observer** is when there is AT LEAST 1 defined type vector and who return a predefined type
+