What is a fictitious force, as distinguished from a real force like tension or friction?

1. A fictitious force is defined as a force having no physical origin. 2. It arises only because an observer is using a non-inertial, accelerating or rotating frame of reference rather than an inertial one. 3. It is not restricted to pushing only, nor is it defined by acting solely on rotating objects, and it has no fixed size relative to gravity. 4. The defining feature is the absence of a real physical source, which is exactly what separates it from forces like tension, friction, or gravity. _Source: OpenStax College Physics (CC BY 4.0), Ch 6 "Uniform Circular Motion and Gravitation", section 6.4 Fictitious Forces and Non-inertial Frames: The Coriolis Force_