If you are looking for the noun definitions and differences, I hope this helps. A dock is usually the space or waterway between two piers. A harbor is a place along the shore that is deep enough for boats to dock, and thus provide protection from the wind and waves. Some harbors are natural and have no piers. A pier is a wooden jetty made of wood that sticks out into the water from land. It is usually built on posts and is for docking ships. A port is any city, town, or place where ships load and unload. Keep in mind the words dock and harbor can also be used as verbs and their meanings are different than those of the nouns. ~Samanth