Arid. The word "arid" indicates an extremely dry climate.

Gemini. The Clown Face Nebula is also in the Gemini constellation.

Rotorcraft. A rotorcraft uses lift created by rotor blades.

Nikola Tesla. Tesla was an inventor, mechanical engineer and electrical engineer.

England. A CAT scan is a series of x-rays that are assembled by a computer to create detailed images.

P. Sometimes animals can actually hear the P waves of an earthquake before the waves are felt.