Deuterium is one of the isotopes of hydrogen.

Hansel and Gretel is my favorite fairy tale.

I am planning to go to Rotterdam next week.

He left a will.

He is majoring in philosophy at university, but he is a typical example of a 'learned fool'.

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.