When HIV disease was first recognized in the early 1980s, it was called AIDS. Today, the term "HIV disease" is a more accurate description of the condition. However, the term AIDS is still used, primarily for the purpose of counting infections and as a description for advanced-stages of HIV disease. AIDS refers to individuals who have particular AIDS-defining conditions such as a very low CD4 white blood cell or specific opportunistic illnesses.
Acquired - the disease is not hereditary but develops after birth from contact with a disease causing agent (in this case, HIV). HIV is not a condition passed on genetically; a person has to become infected with it.
Immunodeficiency - the disease is characterized by a weakening of the immune system.
Syndrome - a group of symptoms that collectively indicate or characterize a disease. In the case of AIDS this can include the development of certain infections and/or cancers, as well as a decrease in the number of certain cells (CD4 T cells) in a person’s immune system.