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.

He is writing a thesis on monotheism.

General relativity is a theory of physics proposed by Einstein.

Special relativity is one of the fundamental theories of physics.

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