Completeness

Logic

The completeness of the real numbers, which implies that there are no "holes" in the real numbers
Complete metric space, a metric space in which every Cauchy sequence converges
A uniform space is complete if every Cauchy net in it converges (or equivalently every Cauchy filter in it converges)
Complete measure, a measure space where every subset of every null set is measurable
Completion (ring theory) at an ideal
Completeness (statistics), a statistic that does not allow an unbiased estimator of zero
Complete graph, an undirected graph in which every pair of vertices has exactly one edge connecting them
Complete category, a category C where every diagram from a small category to C has a limit; it is cocomplete if every such functor has a colimit
Completeness (order theory), a notion that generally refers to the existence of certain suprema or infima of some partially ordered set
Complete algebraic variety, an algebraic variety that satisfies an analog of compactness.
Complete set of commuting operators (or CSCO), a set of commuting operators in quantum mechanics whose eigenvalues are sufficient to specify the physical state of a system
Complete orthonormal basis—see Orthonormal basis#Incomplete orthogonal sets

Complete (complexity), a notion referring to a problem In computational complexity theory that all other problems in a class reduce to.
Completeness (knowledge bases), found in knowledge base theory.
Complete search algorithm, a search algorithm that is guaranteed to find a solution if there is one

Complete flower, a flower with both male and female reproductive structures as well as petals and sepals. See Sexual reproduction in plants.