Set
A set is any well-defined, unordered collection of objects (also called elements or members).
Element
Elements are typically mathematical objects of any kind: numbers, symbols, points in space, lines, other geometrical shapes, variables, or even other sets.
Tuple
A tuple is a finite sequence or ordered list of elements. An n-tuple is a tuple of n elements, where n is a non-negative integer. There is only one 0-tuple, called the empty tuple. A 1-tuple and a 2-tuple are commonly called a singleton and an ordered pair, respectively.