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Douglas Harper's Etymology Dictionary

1928, from red(uction) + ox(idation).


n. (context chemistry English) a reversible process in which one reaction is an oxidation and the reverse is a reduction


n. a reversible chemical reaction in which one reaction is an oxidation and the reverse is a reduction [syn: oxidation-reduction, oxidoreduction]


Redox is a contraction of the name for a chemical reduction–oxidation reaction. Any such reaction involves both a reduction process and a complementary oxidation process. Redox reactions include all chemical reactions in which atoms have their oxidation state changed; in general, redox reactions involve the transfer of electrons between chemical species. The chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. Oxygen is not necessarily included in such reactions as other chemical species can serve the same function.

The term "redox" comes from two concepts involved with electron transfer: reduction and oxidation. It can be explained in simple terms:

  • Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
  • Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, these are only specific examples of a more general concept of reactions involving electron transfer.

Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid–base reactions. Like acid–base reactions, redox reactions are a matched set, that is, there cannot be an oxidation reaction without a reduction reaction happening simultaneously. The oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction. When writing half-reactions, the gained or lost electrons are typically included explicitly in order that the half-reaction be balanced with respect to electric charge.

Though sufficient for many purposes, these descriptions are not precisely correct. Although oxidation and reduction properly refer to a change in oxidation state — the actual transfer of electrons may never occur. The oxidation state of an atom is the fictitious charge that an atom would have if all bonds between atoms of different elements were 100% ionic. Thus, oxidation is best defined as an increase in oxidation state, and reduction as a decrease in oxidation state. In practice, the transfer of electrons will always cause a change in oxidation state, but there are many reactions that are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds).

There are simple redox processes, such as the oxidation of carbon to yield carbon dioxide (CO) or the reduction of carbon by hydrogen to yield methane (CH), and more complex processes such as the oxidation of glucose (CHO) in the human body through a series of complex electron transfer processes.

Redox (disambiguation)

Redox refers to the chemical reduction-oxidation reaction. It may also refer to:

  • Redox OS, an operating system written in the Rust programming language
  • Redox Brands, a company established in 2000 in Ohio, United States, merged in 2006 to CR Brands
  • Redox titration, a type of titration based on a redox reaction between the analyte and titrant

Usage examples of "redox".

CO before the freed hydrogen made a nuisance of itself, interfering with the redox we use in the city and on board here.

The discovery that this life form could use only gaseous oxygen, rather than nitrates, in its redox energy machinery had driven the Observer on a frantic search for another unit to which the knowledge could be transferred.

The result, since there’s never been any way to stop people from using knowledge once it’s been acquired, is that some folks, and some whole cities, have gone ahead designing and releasing pseudos able to break down water, and others to take the oxygen and react it with CO before the freed hydrogen made a nuisance of itself, interfering with the redox we use in the city and on board here.