The highly influential framework of conceptual spaces provides a geometric way of representing knowledge. Instances are represented by points in a high-dimensional space and concepts are represented by regions in this space. In this article, we extend our recent mathematical formalization of this framework by providing quantitative mathematical definitions for measuring relations between concepts: We develop formal ways for computing concept size, subsethood, implication, similarity, and betweenness. This considerably increases the representational capabilities of our formalization and makes it the most thorough and comprehensive formalization of conceptual spaces developed so far.The parameter W = W ∆ , {W δ } δ∈∆ contains two parts: W ∆ is the set of positive domain weights w δ with δ∈∆ w δ = |∆|. Moreover, W contains for each domain δ ∈ ∆ a set W δ of dimension weights w d with d∈δ w d = 1.The similarity of two points in a conceptual space is inversely related to their distance. This can be written as follows :Sim(x, y) = e −c·d(x,y) with a constant c > 0 and a given metric dBetweenness is a logical predicate B(x, y, z) that is true if and only if y is considered to be between x and z. It can be defined based on a given metric d:The betweenness relation based on d E results in the line segment connecting the points x and z, whereas the betweenness relation based on d M results in an axis-parallel cuboid between the points x and z. One can define convexity and star-shapedness based on the notion of betweenness:Definition 2. (Star-shapedness) A set S ⊆ CS is star-shaped under a metric d with respect to a set P ⊆ S : ⇐⇒ ∀p ∈ P, z ∈ S, y ∈ CS : (B d (p, y, z) → y ∈ S)