Quadrilateral just means "four sides" (quad means four, lateral means side). A Quadrilateral has four-sides, it is 2-dimensional (a flat shape), closed (the lines join up), and has straight sides. In Euclidean plane geometry, a quadrilateral is a polygon with four edges and four vertices. Other names for quadrilateral include quadrangle, tetragon, and 4-gon. There are two properties of quadrilaterals: A quadrilateral should be closed shape with 4 sides. All the internal angles of a quadrilateral sum up to 360 degree. Speed is a very basic concept in motion which is all about how fast or slow any object moves. We define speed as distance divided by time. Speed is inversely proportional to the time taken when the distance travelled is constant. So when speed increases, time decreases and vice versa.