In mathematics, more specifically in functional analysis, a subset ${\displaystyle T}$ of a topological vector space ${\displaystyle X}$ is said to be a total subset of ${\displaystyle X}$ if the linear span of ${\displaystyle T}$ is a dense subset of ${\displaystyle X.}$^[1] This condition arises frequently in many theorems of functional analysis.

Unbounded self-adjoint operators on Hilbert spaces are defined on total subsets.

• Dense subset – Subset whose closure is the whole spacePages displaying short descriptions of redirect targets
• Positive linear operator – Concept in functional analysis
• Topological vector spaces – Vector space with a notion of nearnessPages displaying short descriptions of redirect targets