Ring (mathematics)
Valuation ring

If K is a field, a valuation v is a group homomorphism from the multiplicative group K to a totally ordered abelian group G such that, for any f, g in K with f + g nonzero, v (f + g) ≥ min{ v (f), v (g)}. The valuation ring of v is the subring of K consisting of zero and all nonzero f such that v (f) ≥ 0.

Examples:
detectable_content:postscript, punctuation:no_comma