nonoxygen

Nonoxygen is an informal adjective used to describe something that lacks oxygen or does not contain oxygen. In scientific writing, more precise terms are often preferred, such as deoxygenated, anoxic, non-oxygenated, or non-oxide, depending on the context. The word combines the prefix non- with oxygen, from the Greek oxys and genes, but is not a formal chemical class in itself.

In chemistry, nonoxygen compounds are molecules that do not contain any oxygen atoms. Many organic compounds, such as hydrocarbons (methane, ethane) or chlorinated hydrocarbons, are non-oxygen-containing. Conversely, oxides, carbonates, and many other inorganic species contain oxygen. The term non-oxide is sometimes used to distinguish species that do not include oxygen in their formula.

In biology and environmental science, the related terms oxygen-free or anoxic describe environments with little or no dissolved oxygen. Organisms are categorized as aerobes (oxygen-using) or anaerobes (not requiring oxygen). The phrase nonoxygen often appears in descriptions of deoxygenated tissues, blood, or fluids, and in discussions of non-oxygenic photosynthesis, a form of photosynthesis that does not release oxygen as a byproduct.

Because oxygen is a major element in chemistry and biology, the use of nonoxygen can be ambiguous. When precision matters, specialists prefer terms such as deoxygenated, anoxic, non-oxide, or oxygen-free to convey the exact condition.