This page contains several interrelated definitions, which may ultimately be circular.
A physical quantity is a physical property which can be quantified.
A physical property is any measurable property whose describes the state of a physical system.
A physical system is a portion of the physical universe which has been chosen for investigation for a particular purpose.
A physical process is a physical system whose importance is in the way it changes over time.
A measurable property is a property of a physical system which can be compared against a standard unit of measurement to provide a numerical value defining the quantity of that property.
A quantitative property is a property of a physical system which exists in a range of values corresponding with a number, such that the system can be described as having a particular number of a unit of measurement of that property.
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): quantity