The Clinical Measurement Ontology (CMO), Measurement Methods Ontology (MMO), and Experimental Condition Ontology (XCO) are currently being developed at the Rat Genome Database. For more information about these vocabularies please see Shimoyama et al. Three ontologies to define phenotype measurement data. Front Genet. 2012;3:87. Epub 2012 May 28 or contact us (http://rgd.mcw.edu/contact/index.shtml).
Any measurement in which the number of individuals in a study population that display a disease at a point in time or develop a disease within a determined period of time are compared to the total number of individuals in the study population. Often expressed as a percentage but could be expressed as a ratio.
Comment:
Epidemiologically, incidence specifically refers to "the rate at which a certain event occurs, as the number of new cases of a specific disease occurring during a certain period in a population at risk" (Dorland), but in popular usage it can also be used as a measure of the number of individuals in a population which have a particular condition, i.e. as a synonym for prevalence.