Sickling is a medical condition where red blood cells take on a crescent or sickle shape instead of their normal round shape. There are various synonyms used to describe sickling, including hemoglobinopathy, hemoglobin disorder, and sickle cell anemia. Each of these words describes the same condition, however, they may be used in different contexts depending on the situation of the patient. Other synonyms for sickling, which are sometimes used interchangeably, include sickle cell disease, sickle cell trait, and sickle-thalassemia. Each of these terms refers to specific variations of the condition and is used in specific contexts depending on the type and severity of the illness.