Mach’s principle fits into the wider "relational principle", advocating that not only inertia, but also space and time emerge from the interaction of matter. Con-cepts of a Machian/relational theory are proposed, where inertia and energy are defined as mutual properties between pairs of objects. Due to Berkeley, only ra-dial motion represents kinetic energy between (point) masses, which is the basis of anisotropic inertia, which in turn underlies the relational principle. The New-tonian definition of potential energy is considered a model for Machian inertia, leading to a frame independent definition of Machian kinetic energy, which com-prises of the Newtonian terms (relative to the "fixed stars") and small anisotropic M...