Isohypse is a term used to describe lines that join points on a map that have equal heights above sea level. Other terms that can be used as synonyms for isohypse include contour line, contour, isopleth, and isoline. Contour line is a more commonly used term than isohypse and is widely used in topographical maps. Isolines, on the other hand, can refer to any line on a map that joins points of equal value, such as temperature, rainfall, or pressure. Isopleth, on the other hand, is a term that is used to denote a line that joins points of equal numerical value, often used in scientific and mathematical contexts.