This word requires an apostrophe.

In Greek mythology, Poseidon is known as the god of the sea.

The art and technique of typography play an important role in information transmission.

He is conducting a study on pornography.

Portuguese Guinea was once a Portuguese colony in Africa.

This shirt is made of polynosic, so it's very soft and comfortable.

An opossum is a nocturnal animal.

Porphyrin is a compound that plays an important role in the body.

In organic chemistry, porphin plays an important role.

My new apartment is on the third floor of the co-op.