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

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

We will act according to the Mountain Standard Time.

This shape is called a gyrobifastigium.

He ate three apples.

The character '喰' means to eat.

He is composing a poem.

He is studying late into the night to learn a new computer language.

In linear algebra, triangular matrices play a very important role.

A lower triangular matrix is a matrix where all the elements below the main diagonal are zero.