UML

Unified Modeling Language: a standard visual notation for modeling software, with structure diagrams such as class and component diagrams, and behavior diagrams such as sequence, state and activity

Grady Booch, James Rumbaugh and Ivar Jacobson developed it in the mid-1990s, and the Object Management Group adopted it as a standard in 1997. UML 2 defines 14 diagram types. In practice a few survive into everyday use: sequence, state, class and activity diagrams, usually sketched in a tool like Mermaid rather than drawn to the full specification.