What is Sequence Diagram ?
A sequence diagram simply depicts interaction between objects in a sequential order i.e. the order in which these interactions take place. We can also use the terms event diagrams or event scenarios to refer to a sequence diagram. Sequence diagrams describe how and in what order the objects in a system function. These diagrams are widely used by businessmen and software developers to document and understand requirements for new and existing systems.
Example: A sequence diagram for an emotion based music player:
![](https://media.geeksforgeeks.org/wp-content/uploads/seq19.png)
What is Activity Diagram ?
An Activity Diagram is basically a flowchart (Unified Modelling Language) diagram which is used to describe the dynamic aspect of the system. the flowchart represents the flow of activities from one activity to another activity. The activities can be described as the operation of a System. The flow of control in the activity diagram is drawn from one operation to another. This flow can be sequential, branched or concurrent.
Example: An activity diagram for an emotion based music player
![](https://media.geeksforgeeks.org/wp-content/uploads/UML-Activity-Diagram.png)
Similarities Between Sequence and Activity Diagram:
- Both Sequence Diagram and Activity Diagram are UML diagrams.
- Both Sequence and Activity Diagrams are used to represent the control flow of messages.