circuit-breaker /sk.t bre.k./
noun a small protective device in the circuit which blows or breaks before a dangerous overload of current arises
circuitry /sk.tri/ noun a system of electrical circuits . In an anti-skid brak-ing system, circuitry is employed which can detect individual wheel decelera-tion.
circular /skjυl./ adjective shaped
like a circle . Anodes are circular plates with centre holes. . semi-circu-lar shaped like a half-circle . noun a document distributed to a large number of people . an aeronautical information circular
circular slide rule /skjυl. sla.d rul/ noun a calculating device on which all manner of conversions and complex calculations can be made to assist in flight planning
circulate /skjυle.t/ verb to move round in such a way as to arrive at the point of departure . Water circulates via the radiator and pump through to the engine block itself.
circulation /skjυle..(.)n/ noun
the act of moving round in such a way as to arrive at the point of departure .
The general circulation is indicated by the arrows. . cyclonic circulation the circulation of air which, if viewed from above, is anticlockwise in the northern hemisphere and clockwise in the south-ern hemisphere
circulatory /skjυle.t(.)ri/ adjec-tive moving around a circuit . a self-contained re-circulatory oil system

circumference /s.kmf(.)r.ns/
noun the distance around the edge of a circle . The angle subtended by an arc
equal to one 360th part of the circum-ference of a circle is called one degree.
circumstance /skmstns/ noun a
condition which affects something in a given situation . in some circum-stances, under certain circumstances
in some particular situations cirro-/s.r.υ/ prefix high altitude, i.e. above 20,000 feet
cirrocumulus /s.r.υkjumjυl.s/
noun a layer of broken cloud at about 20,000 feet
cirrostratus /s.r.υstrɑt.s/ noun a
layer cloud at about 20,000 feet cirrus /s.r.s/ noun a high cloud in a mass of separate clouds which are formed of ice crystals
Civil Aviation Authority /s.v.l e.vie..(.)n .θ.r.ti/ noun the organisation which licences operators, aircraft and employees for non-military, especially commercial aviation. Abbre-viation CAA
Civil Aviation Publication /s.v.l e.vie..(.)n pbl.ke..(.)n/ noun a book, etc., published by the Civil Avia-tion Authority, each publication having its own reference number . The proce-dure for obtaining a bearing can be found in CAP 413. Abbreviation CAP
COMMENT: CAA (Civil Aviation Authority) publications are referred to as CAPs and each has a reference number for identification: the procedure for obtaining a bearing is described in CAP 413.