If `R` is a polynomial ring, then the coefficient ring is the base ring from which the coefficients are drawn. If `R` is constructed from a polynomial ring as a quotient ring or a fraction ring or a sequence of such operations, then the original coefficient ring is returned.

i1 : coefficientRing(ZZ/101[a][b]) ZZ o1 = ---[a] 101 o1 : PolynomialRing |

i2 : ultimate(coefficientRing,ZZ/101[a][b]) ZZ o2 = --- 101 o2 : QuotientRing |

- coefficientRing(Ring)
`coefficientRing(LocalRing)`(missing documentation)