Sublinear function

A sublinear function (or functional, as is more often used in functional analysis), in linear algebra and related areas of mathematics, is a function ${\displaystyle f:V\rightarrow \mathbf {F} }$ on a vector space V over F, an ordered field (e.g. the real numbers ${\displaystyle \mathbb {R} }$), which satisfies

${\displaystyle f(x+y)\leq f(x)+f(y)}$  for any x, y ∈ V (subadditivity).

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