(mathematics) A mathematical constant, denoted by Λ, defined via the zeros of a certain function H(λ, z), where λ is a real parameter and z is a complex variable. H has only real zeros if and only if λ ≥ Λ. The Riemann hypothesis is equivalent to the conjecture that Λ ≤ 0.

(graph theory) A theorem stating that, when all finite subgraphs of an infinite graph can be colored using c colors, the same is true for the parent graph.