CircleA set of points in a plane at a fixed distance (the radius) from a fixed point (the centre) also in the plane; alternatively the path traced by a single point travelling in a plane at a fixed distance (the radius) from a fixed point (the centre) in the same plane. One half of a circle cut off by a diameter is a semi-circle. |
CircularIn the form of a circle; perfectly round in two-dimensions. |
CircumferenceThe length of a circle (its perimeter). If the radius of a circle is r units, and the diameter d units, then the circumference is 2 ?r, or ?d units. For a sphere the circumference is the length of a 'great circle' on the sphere - this is like the equator on our planet. |
ClockwiseIn the direction in which the hands of clock travel, and the direction bearings and angles are usually measured. Anti-clockwise or counter-clockwise are terms used for the opposite direction. |
Co-ordinateA position in 2D or 3D space, represented by numbers, letters or both. See 'Cartesian co-ordinates'. |
CoefficientOften used for the numerical coefficient. More generally, a factor of an algebraic term. Example: in the term 4xy, 4 is the numerical coefficient of xy but x is also the coefficient of 4y and y is the coefficient of 4x. |
Common FractionA fraction where the numerator and denominator are both integers. Also known as a simple or vulgar fraction. Contrast with a compound or complex fraction where the numerator or denominator or both contain fractions. See also decimal fraction. |
Complementary NumbersTwo angles with the sum of 90 degrees . |
Compound MeasuresMeasures with two or more dimensions. Examples: speed calculated as distance ÷ time; density calculated as mass ÷ volume; car efficiency measured as litres per 100 kilometres; and rate of inflation measured as percentage increase in prices. |
ConcaveAdjective to describe a line or surface curving inwards (like the shape of a cave). A concave polygon has at least one re-entrant angle i.e. one interior angle greater than 180 degrees . |