State Diagrams give an abstract depiction of the different modes in which an entity or object can exist, and what the allowed transitions are (optionally annotated with mechanisms and/or names for those transitions). There are State Diagrams in UML, SysML, and the sole diagram type in OPM is arguably best described as a hybrid State Diagram/Block Definition Diagram.

Intensive dives into state diagrams gets you into the realm of graph theory in mathematics, like Petri Nets.

Example

Using Mermaid to depict Ice Cream.

stateDiagram-v2
s1: In carton
s4: On_Floor
s1 --> s4 : server dropping
s1 --> In_Cone : serving
In_Cone --> s4 : customer dropping
state In_Cone {
	s2: Firm
	s3: Messy
	s2 --> s3 : melting
}


Source

mermaid - Markdownish syntax for generating flowcharts, sequence diagrams, class diagrams, gantt charts and git graphs.

UML state machine - Wikipedia

Related Notes

UML

SysML

OPM