Meaning : The fifth and highest element after air and earth and fire and water. Was believed to be the substance composing all heavenly bodies.

Meaning : Any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom.

Meaning : A medium that was once supposed to fill all space and to support the propagation of electromagnetic waves.

Meaning : A colorless volatile highly flammable liquid formerly used as an inhalation anesthetic.