UML - Activity Diagram Symbols' Meaning

UML - activity diagram symbols meaning

Activity diagrams are as simple to make as an ordinary flowchart. Each symbol has a meaning and context where its use is appropriate. Check out our guide for a detailed list of UML activity diagram symbols meaning.

To experiment with these symbols, just click the buttons below. Drawing an activity diagram in Lucidchart is fast, easy, and completely free.

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Activity Diagram Symbols' Meaning

UML - activity diagram symbols meaning

The start symbol represents the beginning of a process or workflow in an activity diagram. It can be used by itself or with a note symbol that explains the starting point.

UML - activity diagram symbols meaning

The activity symbol is the main component of an activity diagram. These shapes indicate the activities that make up a modeled process.


UML - activity diagram symbols meaning

The connector symbol is represented by arrowed lines that show the directional flow, or control flow, of the activity. An incoming arrow starts a step of an activity; once the step is completed, the flow continues with the outgoing arrow.


UML - activity diagram symbols meaning

The join symbol, or synchronization bar, is a thick vertical or horizontal line. It combines two concurrent activities and re-introduces them to a flow where only one activity occurs at a time.

UML - activity diagram symbols meaning

A fork is symbolized with multiple arrowed lines from a join. It splits a single activity flow into two concurrent activities.

UML - activity diagram symbols meaning

The decision symbol is a diamond shape; it represents the branching or merging of various flows with the symbol acting as a frame or container.

UML - activity diagram symbols meaning

The note symbol allows the diagram creators or collaborators to communicate additional messages that don't fit within the diagram itself.

UML - activity diagram symbols meaning

The receive signal symbol demonstrates the acceptance of an event. After the event is received, the flow that comes from this action is completed.


UML - activity diagram symbols meaning

The send signal symbol means that a signal is being sent to a receiving activity, as seen above.

UML - activity diagram symbols meaning

The shallow history pseudostate symbol represents a transition that invokes the last active state.

UML - activity diagram symbols meaning

The option loop symbol allows the creator to model a repetitive sequence within the option loop symbol.

UML - activity diagram symbols meaning

The flow final symbol shows the ending point of a process' flow. While a flow final symbol marks the end of a process in a single flow, an end symbol represents the completion of all flows in an activity.

UML - activity diagram symbols meaning

The end symbol represents the completion of a process or workflow.


Using Symbols in an Activity Diagram

In Lucidchart, creating an activity diagram from scratch is surprisingly simple. Just open up the correct shape library, drag out symbols from the toolbox to the canvas, then model the process flow by drawing lines between shapes. It's easy to resize and style any element. You can even import SVG shapes and Visio files for a custom solution. If you'd like some inspiration, visit Lucid U for pre-made templates, examples, and tutorials.


Lucidchart offers standard UML 2.0 shapes, so you can easily make and share activity diagrams. Whether it's for school or work, your UML diagrams will be professional and easy to read. Try it for yourself!

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