1) A syndrome resulting from the acquired deficiency of cellular immunity caused by the human immunodeficiency virus (HIV). It is characterized by the reduction of the Helper T-lymphocytes in the peripheral blood and the lymph nodes; opportunistic infections (usually pneumocystis carinii pneumonia, cytomegalovirus (CMV) infections, tuberculosis, candida infections, and cryptococcosis); and the development of malignant neoplasms (usually non-Hodgkin's lymphoma and Kaposi's sarcoma). The human immunodeficiency virus is transmitted through sexual contact, sharing of contaminated needles, or transfusion of contaminated blood. Generalized lymphadenopathy, fever, weight loss, and chronic diarrhea are common symptoms of AIDS. The patients usually die either of opportunistic infections or malignant neoplasms. -- 2004

2) A disease caused by human immunodeficiency virus (HIV). People with AIDS are at an increased risk for developing certain cancers and for infections that usually occur only in individuals with a weak immune system.