A formal representation of knowledge within a domain that is machine-readable but also understandable to humans; it typically includes unique hierarchically arranged concepts that have specific attributes and are semantically related to other concepts. Source: Dissanayake, P. I., Colicchio, T. K., & Cimino, J. J. (2020). Using clinical reasoning ontologies to make smarter clinical decision support systems: a systematic review and data synthesis. Journal of the American Medical Informatics Association, 27(1), 159-174. https://doi.org/10.1093/jamia/ocz169
An outcome measure is a measure that focuses on the health status of a patient (or change in health status) resulting from healthcare - desirable or adverse.