The symptom ontology was designed around the guiding concept of a symptom being: “A perceived change in function, sensation or appearance reported by a patient indicative of a disease”. Understanding the close relationship of Signs and Symptoms, where Signs are the objective observation of an illness, the Symptom Ontology will work to broaden it’s scope to capture and document in a more robust manor these two sets of terms. Understanding that at times, the same term may be both a Sign and a Symptom. The Symptom Ontology is available under CC0 license (https://creativecommons.org/publicdomain/zero/1.0/).