What characterizes a sailing vessel?

A sailing vessel is primarily characterized by its method of propulsion, which relies on sails to harness wind power. When a sailing vessel is under sail and has no engine in operation, it is operating in the traditional manner for which these vessels were designed, relying solely on wind to move through the water. This definition is fundamental to understanding sailing vessels, as it differentiates them from other types of boats that may use engines or a combination of power sources.

While other options describe different aspects of vessels, they do not fit the definition of a sailing vessel. A vessel that is under power from machinery indicates it's a powerboat, not a sailing vessel. Using both wind and engine power describes a hybrid or motor-sailer type of vessel. Lastly, being tied to a dock doesn't pertain to the operational characteristics of the sail, but rather to the status or location of any vessel at a given moment. Thus, the essence of a sailing vessel lies in its ability to move solely using sails without any engine assistance.