It's difficult to understand the principles of electrooptics.

I am majoring in econometrics at university.

This shape is called a muoctahedron, in other words, a hexagonal four-piece square hole twisted polyhedron.

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

My cat has been infected with the feline immunodeficiency virus.

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.

Cell biology is the study of the structure and function of cells, which are the basic units of life.

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