Human immunodeficiency virus -LRB- HIV -RRB- is a lentivirus -LRB- a member of the retrovirus family -RRB- that causes acquired immunodeficiency syndrome -LRB- AIDS -RRB- , a condition in humans in which the immune system begins to fail , leading to life-threatening opportunistic infections .

Human immunodeficiency virus -LRB- HIV -RRB- is a retrovirus that infects the human immune system .
