New Proposal for Lightspeed Definition

I have been grappling, in this blog, with defining the similar concepts: Velocity, Lightspeed, Momentum and Inertia.  One of my priorities right now is to bring order to these by establishing strict definitions.  The following is my latest proposal for Lightspeed:

Lightspeed is one light unit's distance change with no direction change per time change

Paul Wharton
Father of Metachemics