A probabilistic functional 3D scene graph is a structured representation of a three-dimensional physical environment that models the operational and interactive relationships among objects and parts while explicitly quantifying uncertainty over those connections. Unlike conventional 3D scene graphs that primarily record spatial arrangements and static geometry, functional graphs capture actionable affordances, operational dependencies, and usage roles across entities in a scene. By incorporating probabilistic modeling, this representation evaluates the likelihood of relations holistically across the environment, leveraging semantic priors and geometric constraints to resolve ambiguities and assign calibrated confidence scores to predicted interactions.