Units of length (non-metric): inch/mile/yard

Parts of the eye: cornea/iris/retina

Constellations that are used in the zodiac: Aries/Libra/Pisces

Geometrical shapes: circle/decagon/triangle

Ten most common elements in the universe: iron/neon/nitrogen

Bones of the human body: femur/sternum/ulna

Planets: Earth/Mars/Venus

Birthstones: opal/pearl/ruby

Fruit: grape/peach/tangerine

Quark flavors: charm/strange/top

Dog breeds: pointer/poodle/Samoyed

Last names of famous scientists who won the Nobel Prize in Physics: Curie/Einstein/Marconi