a plane figure with three straight sides and three angles.
rectangle:
a plane figure with four straight sides and four right angles, especially one with unequal adjacent sides, in contrast to a square.
circle:
round plane figure whose boundary (the circumference) consists of points equidistant from a fixed point (the centre).
cylinder:
solid geometrical figure with straight parallel sides and a circular or oval cross section.
cone:
surface or solid figure generated by the straight lines which pass from a circle or other closed curve to a single point (the vertex) not in the same plane as the curve.
