Qualities can be seen as the basic entities we can perceive or measure: shapes, colors, sizes, sounds, smells, as well as weights, lengths, electrical charges... 'Quality' is often used as a synonymous of 'property', but this is not the case in this upper ontology: qualities are particulars, properties are universals. Qualities inhere to entities: every entity (including qualities themselves) comes with certain qualities, which exist as long as the entity exists.