OSI model

This term refers to a theoretical blueprint rather than a physical piece of hardware. It is used primarily by network engineers and students to provide a common language for describing how different protocols interact. Because it is a conceptual framework, it is often contrasted with the TCP/IP model, which is the actual practical implementation used in the modern internet.

In technical discourse, the term is almost always used in the singular when referring to the framework as a whole. While one might discuss the individual layers within the model, the model itself remains a singular conceptual entity.