Aset whose elements belong to a given set element 2 . a number that can be written as a ratio in fraction form irrational number 3 . a number that, when in decimal form, does not terminate or repeat rational number 4 . a number that can be written as an infinite decimal real number 5 . a collection or group of objects set 6 . a diagram that shows the relationships between sets subset 7 . an object that belongs to the set; also called a member venn diagram