x1 is a physically-required conserved quantity in an ideal closed system such that it is associated with (Noetherian) symmetry/Hamiltonian-commuting observable/deterministic feature/law/property/aspect x2, applicable under conditions/in universe/in metaphysics x3
See also: impetu, nejni, nejnimpetu, cnampetu, dikca, eldicka'u, kuardicka'u, tcelerita.