section_path: Specific kinds of variables/Examples
section_name: Examples
paragraph_text: Examples
  
  If one defines a function f from the real numbers to the real numbers by
  
  then x is a variable standing for the argument of the function being defined, which can be any real number.
  
  In the identity
  
  the variable i is a summation variable which designates in turn each of the integers 1, 2,..., n (it is also called index because its variation is over a discrete set of values) while n is a parameter (it does not vary within the formula).
  
  In the theory of polynomials, a polynomial of degree 2 is generally denoted as ax + bx + c, where a, b and c are called coefficients (they are assumed to be fixed, i.e., parameters of the problem considered) while x is called a variable. When studying this polynomial for its polynomial function this x stands for the function argument. When studying the polynomial as an object in itself, x is taken to be an indeterminate, and would often be written with a capital letter instead to indicate this status.