Ameasurement must include both a number blank

... AND A UNIT .

If I tell you that I have a piece of string that's 71 long, you still have no idea what I'm talking about until I tell you if that's millimeters, centimeters, inches, meters, feet, yards, smoots, kilometers, leagues, miles, furlongs, nanometers, Mach-seconds, chains, parsecs, light years etc.

some think that theories become laws, but theories and laws have separate and distinct roles in the scientific method. a law is a description of an observed phenomenon in the natural world that hold true every time it is tested. it doesn't explain why something is true; it just states that it is true.

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.