This research deals with analyzing expressions of disease which have been considered as a semantic field for a group of expressions entitled as disease in Kitab Al-Alfadh by Ibn As-Sikkeet, a book listed as a dictionary of meaning.When we figured the expressions related to our study-synonyms of disease and its symptoms, we found that the writer had subjected some expressions to the semantic grading while some other expressions are not, for which we explained the purpose. Moreover, we gave our viewpoint about the grading of some expressions and explained the symptoms of each disease. This has been summarized in a four-columns table to explain the effort of the Arab scientists as pioneers in this field of knowledge.