Before revision: In medicine, comorbidity —from Latin morbus ("sickness"), co ("together"), -ity (as if - several sicknesses together)—is the presence of one or more additional conditions often co-occurring (that is, concomitant or concurrent) with a primary condition.
After revision: In medicine, comorbidity refers to the simultaneous presence of two or more medical conditions in a patient; often co-occurring (that is, concomitant or concurrent) with a primary condition.