CIR may refer to:
The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis.
Cirrhosis is a condition in which the liver does not function properly due to long-term damage. Typically, the disease comes on slowly over months or years.
Cirque du Soleil (pronounced: [sɪʁk dzy sɔ.lɛj], "Circus of the Sun") is a Canadian entertainment company.
A circadian rhythm /sɜːrˈkeɪdiən/ is any biological process that displays an endogenous, entrainable oscillation of about 24 hours.
A circus is a company of performers that may include clowns, acrobats, trained animals, trapeze acts, musicians, hoopers, tightrope walkers, jugglers, unicyclists, as well as other object manipulation and stunt-oriented artists.
The Circassians (Circassian: Адыгэхэр, Adygekher) are a Northwest Caucasian ethnic group native to Circassia, many of whom were displaced in the course of the Russian conquest of the Caucasus in the 19th century, especially after the Russian–Circassian War in 1864. In its narrowest sense, the term "Circassian" includes the twelve Adyghe (Circassian: Адыгэ, Adyge) tribes (three democratic and nine aristocratic), i.e.
A circle is a simple closed shape in Euclidean geometry. It is the set of all points in a plane that are at a given distance from a given point, the centre; equivalently it is the curve traced out by a point that moves so that its distance from a given point is constant.
In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit.