A port city refers to a city that has a harbor, where ships dock, load and offload cargo or passengers. Sometimes the term is used interchangeably with "seaport," which is a city that serves as a gateway to the sea. Other synonyms for port city include "coastal city," "harbor city," and "seaside city." Some examples of famous port cities include New York City, Singapore, Rotterdam, and Shanghai. These types of cities are often considered gateways to international trade and tourism, as well as vital hubs for transportation and commerce. Regardless of the term used, port cities form a critical link between nations and people, with a vital role to play in today's global economy.