What is referred to as the path a vessel is expected to follow?

The term that describes the path a vessel is expected to follow is "Route." A route outlines the specific path that a vessel intends to take from one point to another, taking into consideration navigational aids, obstacles, and characteristics of the waterway. It represents a planned directional journey that helps in safe navigation and compliance with maritime rules.

In contrast, 'Course' typically refers to the direction in which the vessel is steered at any given moment, while 'Heading' indicates the direction in which the vessel's bow is pointing. 'Track line' generally refers to the actual path a vessel has taken through the water as represented on a navigational chart. Hence, while these terms are related to navigation, "Route" is specifically used to denote the expected path a vessel is intended to follow.