This new software maintains upward compatibility with the old version.

These two software have complete interchangeability.

Cats are digitigrade animals, they walk on their toes.

He learned about unguligradism in his zoology class.

His research mainly focuses on the plantigradism of mammals.

She has polycystic ovary syndrome.

Sufficient caution is necessary when handling radioactive materials.

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.