Psychro

Psychro is a combining form used in scientific vocabulary to denote cold or cold-related phenomena. It derives from the Greek psychros meaning cold and is used to form a range of terms across biology, meteorology, and physics. It is not a standalone English word, but rather a prefix or thematic element in compound words.

Common uses include psychrophiles, microorganisms that grow best at cold temperatures, usually near or below 15 °C; psychrotolerant organisms that can grow at low temperatures but have higher optimums; and the field of psychrometry, the study and measurement of moist air and its temperature relationships. A standard instrument is the psychrometer, which uses dry-bulb and wet-bulb readings to determine humidity. The broader field of psychrometry investigates the properties and behavior of air-vapor mixtures under varying temperatures.

In contrast to cryo-, which denotes extreme cold or cryopreservation, psychro- is typically used for cool to cold environments and organisms rather than freezing contexts. The prefix is widely used in ecology, microbiology, and atmospheric science to describe cold-adapted states and processes.