A polynomial of order is a function described by the following expression:
where
are coefficients of the polynomial.
A polynomial of order 
is the simplest type of polynomial. Its chart, 
against , is a line.
Polynomials are used in regression analysis, multiple regression, time series analysis. In a sense, polynomials are the first choice models for various smooth functions, and they are often used for approximation and interpolation of continuous functions. Polynomials are also used as building blocks for splines.
Besides the 1-dimensional polynomials described above, there are extensions to 2-dimensional cases (where the polynomial is a function 
of two variables), and to a higher number of dimensions.
See also short courses