Functional analysis is a branch of mathematics that studies the properties of functions in infinite-dimensional spaces.

The Mesolithic is the era between the Paleolithic and the Neolithic.

The Riemann sum is a method for approximately calculating the integral of a function.

I stabbed the needle for the injection.

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.

He left early to avoid the problem.

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.

The feline immunodeficiency virus can potentially have serious effects on a cat's health.