The different instances in the same class differ in the number of importers and exporters.
Sometimes, even different parts of the same ground layer differ in the number of subdivisible layers.
The CNT differ in the number of walls and different properties.
Most elements exist in different atomic forms that are identical in their chemical properties but differ in the number of neutral particles i.e., neutrons in the nucleus.
Second, puzzles differ in the number and richness of extraneous features (e.g. different colors, stains, line markers) that add significantly to the difficulty.
Isotopes are atoms of the same element that differ in the number of neutrons.
They differ in the number of wires they have, the thickness of the wires and the length of the cord.
Fruit flies from the same species differ in the number of bristles on their bellies; stalk-eyed flies differ in the lengths of their eye stalks.
Members of the subfamily differ in the number of stamens.
They differ in the number of distillation columns that are used; either two or three.
They differ in the number, volume and geometry of their partition cells.
