I actually agree completely with A ki but I suspect you don t actually realize what he she just said A ki really just restated what I had written when I edited the article summary a while back In common usage the term inertia is sometimes also used to refer to an object s momentum or to describe its amount of resistance to change which is technically the same as its mass It is important to understand that these uses of the term are not the same as Newton s more fundamental description of inertia as a principle of the way the universe works which is not a measurable thing In other words some people sometimes use the term inertia to refer to other things than the principle of inertia However the principle of inertia is still an important and valid principle and is the primary meaning of the term In many cases one needs to use context to determine whether somebody is referring to the principle or to something else but I think we ve pretty well established from the conversation above that we re talking about the principle of inertia here not the conventional but inaccurate other uses of the term A ki please tell me if I have misinterpreted your statement