He is working as a behind-the-scenes assistant at the theater.

He heard the clattering sound of the machine being hit.

This pattern is very beautiful, isn't it?

There was no trace of him in his room, as if to make one forget that he had been there.

General relativity is a theory of physics proposed by Einstein.

Special relativity is one of the fundamental theories of physics.

This area is seriously contaminated with radioactive isotopes.

He feels dizzy when he stands up suddenly due to orthostatic hypotension.

My father was diagnosed with ankylosing spondylitis.

In organic chemistry, pyruvic acid plays an important role.