A triangle in which two sides have the same length and consequently two angles are equal. This definition includes an equilateral triangle as a special case.

Symbol: kg. The base unit of mass in SI units ('Système International d'Unités' in French, also known as metric). 1kg. = 1000g.

Symbol: km. A unit of length in SI units ('Système International d'Unités' in French, also known as metric). 1km. = 1000m.

A set of adjacent points that has length but no width. A curve. A straight line is completely determined by two of its points, say A and B. The part of the line between any two of its points is a line segment.

A line drawn on a scatter graph to represent the best estimate of an underlying linear relationship between the variables.

In algebra, an adjective describing an expression, equation or relationship of degree one. Example: 2x + 3y = 7 is a linear equation. This linear equation with its two variables, x and y, can be represented as a straight line graph. The relationship between x and y is linear.

Symbol: l. A metric unit used for measuring volume or capacity. A litre is equivalent to 1000 cubic centimetres

The set of all points that satisfy given conditions. Example: in 3-D the locus of all points that are a given distance from a fixed point is a sphere. Plural: loci.