The

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

is a geologic period. Quaternary (an adjective meaning "fourth in order" or "composed of four items") may also refer to: *

Quaternary (chemistry) Quaternary is a term used in organic chemistry to classify various types of compounds (e. g. amines and ammonium salts).Paula Yurkanis Bruice: ''Organic Chemistry'', Pearson Education Inc., 2004, 4. Ed., p. 78, 104, 893, and 912, . {{clear See ...

(see also

Quaternary compound In chemistry, a quaternary compound is a compound consisting of exactly four chemical elements. In another use of the term in organic chemistry, a quaternary compound is or has a cation consisting of a central positively charged atom with four ...

and

Quaternary phase In materials chemistry, a quaternary phase is a chemical compound containing four elements. Some compounds can be molecular or ionic, examples being chlorodifluoromethane () sodium bicarbonate (). More typically quaternary phase refers to exte ...

) *

Quaternary structure Protein quaternary structure is the fourth (and highest) classification level of protein structure. Protein quaternary structure refers to the structure of proteins which are themselves composed of two or more smaller protein chains (also refe ...

of proteins *

Quaternary sector of the economy The quaternary sector of the economy is based upon the economic activity that is associated with either the intellectual or knowledge-based economy. This consists of information technology; media; research and development; information-based servi ...

, which encompasses knowledge-based services * Quaternary care, health care that includes highly specialized or experimental treatments *

Quaternary numeral system A quaternary numeral system is base-. It uses the digits 0, 1, 2 and 3 to represent any real number. Conversion from binary is straightforward. Four is the largest number within the subitizing range and one of two numbers that is both a sq ...

(base-4) in mathematics * Quaternary counting system, as used in some human languages * ''Quaternary'' (EP), an album by Mötley Crüe

See also