The amount by which the value of a meteorological element differs from the normal value.

1. The distance between two meridians at any given parallel of latitude, expressed in linear units, usually nautical miles; the distance to the east or west made good by a craft in proceeding from one point to another.

2. The point at which reckoning of a voyage begins; usually established by bearings of prominent landmarks as the vessel clears a harbor and proceeds to sea; when a person establishes this point, he is said to take departure. Also known as point of departure.

3. Act of departing or leaving.