The human immunodeficiency virus destroys the immune system, causing the body to lose its ability to fight disease.

The human immunodeficiency virus is the virus that causes AIDS.

He left early to avoid the problem.

This mutetrahedron plays a very important role in the world of mathematics.

This is a 六角四片四角孔ねじれ正多面體, in other words, a muoctahedron.

This is a model of a muoctahedron.

He is suffering from acquired immune deficiency syndrome (AIDS).

This is a model of a mutetrahedron.

This mutetrahedron has a very unusual shape.

He is always working busily.