Similarity, one of six Gestalt principles, is one of the most intuitive ways to perceive the world and categorise the objects surrounding us. The notion of similarity plays an important role in many areas, and it is important to simulate human perception of similarity in order to obtain satisfying results in various applications. We draw our inspiration from Tversky’s work on similarity and define property-based similarity for ontological concepts taking into account their common and distinctive features and their values. We also discuss some possible ways to improve the property-based similarity.