👉 In mathematics, a subtrifid is an operator defined on a Hilbert space that acts as a contraction. A subtrifid is a generalization of the concept of a projection onto a subspace in linear algebra and functional analysis. A subtrifid can be thought of as a continuous function from a closed subspace of a Hilbert space to itself, such that it is zero on the boundary of the subspace. It satisfies certain properties, including the property that it maps
