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Monomial


A monomial is a product of nonnegative integer powers of a fixed set of variables, possibly together with a nonzero coefficient, e.g., x, 3xy^2, or -2x^2y^3z. A monomial can also be thought of as a nonzero summand of a polynomial (Becker and Weispfenning 1993, p. 191). A monomial with the coefficient excluded is usually called a term.

Another common convention reserves "monomial" for the product with its coefficient omitted and uses "term" for a summand including its coefficient (Cox et al. 1997, p. 2). This convention is used in the definitions of leading monomial, leading term, and polynomial reduction. It is necessary to specify the convention when comparing sources.

The Wolfram Language command MonomialList[poly, {x_1, x_2, ...}] gives the list of monomials with respect to the variables x_i in the specified polynomial.

The monomials 1,z,z^2,... form an orthogonal family on the unit circle in the complex plane with respect to angular measure (Dumitriu et al. 2007). For nonnegative integers k and l, writing z=e^(itheta) gives

 int_0^(2pi)(e^(itheta))^k(e^(itheta))^l^_dtheta=int_0^(2pi)e^(itheta(k-l))dtheta=2pidelta_(k,l),
(1)

where delta_(k,l) is the Kronecker delta.

The monomial symmetric polynomials m_lambda, also called monomial functions, sum all distinct monomials obtained by permuting an exponent list. For a partition lambda with at most n parts, pad it with zeros to length n and write

 m_lambda(x_1,...,x_n)=sum_(alpha in O_lambda)product_(j=1)^nx_j^(alpha_j),
(2)

where O_lambda is the set of distinct permutations of that list (Dumitriu et al. 2007). For example, in three variables,

 m_((2,1,1))(x_1,x_2,x_3)=x_1^2x_2x_3+x_1x_2^2x_3+x_1x_2x_3^2.
(3)

Care is needed when consulting the literature, since the distinction between terms and monomials is not always observed. For example, Dummit and Foote (2004, p. 234) define a monomial as a polynomial with only one nonzero term, without defining what is meant by "term."


See also

Binomial, Coefficient, Gröbner Basis, Leading Monomial, Leading Term, Monic Polynomial, Monomial Ideal, Monomial Order, Monomial Symmetric Polynomial, Polynomial, Polynomial Reduction, Term, Trinomial, Variable, Weighted Homogeneous Polynomial

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References

Becker, T. and Weispfenning, V. Gröbner Bases: A Computational Approach to Commutative Algebra. New York: Springer-Verlag, 1993.Cox, D.; Little, J.; and O'Shea, D. Ideals, Varieties, and Algorithms: An Introduction to Computational Algebraic Geometry and Commutative Algebra, 2nd ed. New York: Springer-Verlag, 1997.Dumitriu, I.; Edelman, A.; and Shuman, G. "MOPS: Multivariate Orthogonal Polynomials (Symbolically)." J. Symb. Comput. 42, 587-620, 2007. https://doi.org/10.1016/j.jsc.2007.01.005.Dummit, D. S. and Foote, R. M. "Examples: Polynomial Rings, Matrix Rings, and Group Rings." §7.2 in Abstract Algebra, 3rd ed. Hoboken, NJ: Wiley, pp. 233-238, 2004.

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Monomial

Cite this as:

Weisstein, Eric W. "Monomial." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Monomial.html

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