The description of sound requires the definition of categories that can be obtained in various ways, e.g. by taking into account semantic, phenomenological, perceptual, psychoacoustic and ecological features. Once established, categories may lead to sound ontologies, intended as collections of sounds organized into a hierarchy. In sound design, ontologies can help prepare and create classification spaces that will be later implemented in the tools adopted by sound designers. Multiple ontologies can be created by looking at the same collection of elements, each one reflecting on the abstraction processes employed in identifying the dimensions used for the classification task.