In everyday conversation, these terms are often used interchangeably. That is understandable. They all describe ways of making work repeatable.
Litbox uses operating system as the broader term. An SOP is one part of the operating system. A workflow is another. The operating system connects them to roles, decisions, business memory, tools, training, and real operating context.
You do not need to adopt new jargon. If your team calls it “the way we do things,” Litbox can start there.