diff --git a/Intro_to_Solid.md b/Intro_to_Solid.md
index 32c79c5..4522e8b 100644
--- a/Intro_to_Solid.md
+++ b/Intro_to_Solid.md
@@ -174,3 +174,12 @@ That will be more simple to do extension.
 
 ### Liskov Substitution Principle
 
+This convention tells us to create a substitutable subclass for their parents.
+So, if you want to create an object in the subclass, you have to be able to pass it in the interface.
+
+### Interface Segregation Principle
+
+The _Interface Segregation Principle_ means that all interfaces have to be separated.
+That means that clients has not functions that they do not need.
+
+### Dependency Inversion Principle