Where does matter collide?

The underlying stuff that persists through change and takes on form to become a particular thing, as opposed to the form that makes it what it is. Aristotle's Physics (ca. 350 B.C.E.) introduced this contrast, calling the shapeless substrate hyle and pairing it with form in his account of how things come to be, and his wider metaphysics pushed the idea to a limiting case, a prime matter with no form of its own. The referent is a principle in an analysis of being, the potential that form actualises, and it is not a measurable physical quantity, a printer's composed type, or a question tried in a court.[1]

Unit

A principle in the analysis of a particular thing, the substrate paired with its form

Recovery means

Not applicable

Measured by

Identified by philosophical analysis, by separating what a thing is made of from the form that makes it that thing

That which has mass and takes up space, the substance of physical bodies. Newton's Principia (1687) gave the idea its first measurable form, defining the quantity of matter in a body as the product of its density and its volume, a quantity now called mass, and Einstein's 1905 paper on whether a body's inertia depends on its energy content later showed that this mass is equivalent to energy, so that matter and energy convert into one another. The referent is a physical quantity carried by bodies and scaled in kilograms, distinct from a formless philosophical substrate, a printer's set type, or a question before a court.[2][3]

Unit

A body's quantity of matter, its mass, scaled in kilograms

Recovery means

Not applicable

Measured by

Determined by weighing against a mass standard or from a body's inertial and gravitational response