Background: The words disease, illness and sickness are overlapping and not wholly synonymous. Illness, disease, and sickness characterize different aspects of morbidity and must be dealt with as different phenomena. Changes in one aspect may not relate to changes in another. Despite the widespread use of these terms they are utilized improperly and ambiguously making confusion in the representation of medical knowledge. These terms are improperly used by medical personnel and epidemiologists and little literature dealt with this issue.
Methods: A literature search was conducted on PubMed and Google Scholar. The following search terms were used in different combination “definition,” “disease,” “illness,” “sickness,” “morbidity,” “syndrome,” “disorder,” “predisease,” and “co-morbidity”. A manual search was done in textbooks of public health, community medicine and epidemiology. The most relevant and recent literature were included in the review.
Results: This short review summarizes the definition, the limitations, the overlap and the differences between disease, illness, sickness and the other related terms.
Conclusion: There is a need for a measurable operational definition of disease, illness, sickness and the other related terms to be appropriate for epidemiologists and clinicians as well as applicable in both hospital and community settings.