AIDS (acquired immunodeficiency syndrome): the disease that can result from infection with HIV (human immunodeficiency virus). It is incorrect to refer to the AIDS virus (the virus is HIV, not AIDS), AIDS-infected people (people are infected with HIV, not AIDS) or AIDS test (it is not possible to test for AIDS).

HIV (human immunodeficiency virus): the virus that causes AIDS. Note that not all people who are HIV-positive have AIDS.