(graph theory) the number of vertices in a maximum independent set of a given graph, often denoted as 𝛼=𝛼(G)

(graph theory) the number of edges in a maximum matching, often denoted 𝜈=𝜈(G)

(graph theory) The number of vertices in a minimum vertex cover of a graph, often denoted as 𝜏=𝜏(G).

(graph theory) the number of vertices in a minimum dominating set of a given graph, often denoted as 𝛾=𝛾(G)

plural of telephone number

(mathematics) A numeral system that uses digits to establish a bijection between finite strings and the positive integers, especially by k-adic notation such as unary and decimal without a zero.

plural of number line

(mathematics) A line that graphically represents the real numbers as a series of points whose distance from an origin is proportional to their value

(physics) A Reynolds number at which the flow of a fluid changes from laminar to turbulent.

(topology, algebraic topology) Any of a sequence of numbers, denoted bₙ, which characterise a given topological space K by giving, for each dimension, the number of holes in K of said dimension; (formally) the rank of the nth homology group, Hₙ, of K.