This is a model of a great icosahemidodecahedron.

It is important to learn about the prevention and treatment of the human immunodeficiency virus.

The human immunodeficiency virus destroys the immune system, making the body unable to fight disease.

He is an expert in nuclear physics.

He has already finished writing the report, so we use the present perfect form.

This Chaban Kyogen is a historical form of theater performed improvisationally.

Modern kana usage is one of the notation methods of the Japanese language.

He is attending a programming school to learn object-oriented languages.

She is learning the grammar of the present progressive form.

Learning Modern English is important for smooth international communication.