Classical element

The classical elements typically refer to earth, water, fire, air, and (later) aether which were proposed to explain the nature and complexity of all matter in terms of simpler substances. Ancient cultures in Greece, Angola, Tibet, India, and Mali had similar lists which sometimes referred, in local languages, to "air" as "wind", and to "aether" as "space".

These different cultures and even individual philosophers had widely varying explanations concerning their attributes and how they related to observable phenomena as well as cosmology. Sometimes these theories overlapped with mythology and were personified in deities. Some of these interpretations included atomism (the idea of very small, indivisible portions of matter), but other interpretations considered the elements to be divisible into infinitely small pieces without changing their nature.

While the classification of the material world among the ancient Indians, Hellenistic Egyptians, and ancient Greeks into air, earth, fire, and water was more philosophical, scientists of the Middle Ages used practical, experimental observation to classify materials. In Europe, the ancient Greek concept, devised by Empedocles, evolved into the systematic classifications of Aristotle and Hippocrates. This evolved slightly into the medieval system, and eventually became the object of experimental verification in the 17th century, at the start of the Scientific Revolution.

Modern science does not support the classical elements to classify types of substances. Atomic theory classifies atoms into more than a hundred chemical elements such as oxygen, iron, and mercury, which may form chemical compounds and mixtures.