The term "vessel not under command" means a vessel which through some exceptional circumstance is unable to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel.

The word "underway" means that a vessel is not at anchor, or made fast to the shore, or aground.

Two vessels: left - "Attract the attention of another vessel"; right - power-driven vessel.

Two vessels: left - sailing vessel; shall keep out of the way; right - vessel engaged in mine clearance.

The term "power-driven vessel" means any vessel propelled by machinery.

Vessels shall be deemed to be in sight of one another only when one can be observed visually from the other.

Tug & tow; 50 metres or more; astern > 200 metres in length shall keep out of the way of the fishing vessel.

Two vessels: left - "I am altering my course to port"; right - a vessel engaged on pilotage duty at anchor; 50 metres or more.

A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction.

The words "length" and "breadth" of a vessel mean her length overall and greatest breadth.

Two vessels: left - fishing vessel other than a trawler; shall keep out of the way; right - restricted in her ability to manoeuvre.

The term "seaplane" includes any aircraft designed to maneuver on the water.

Two vessels: left - power-driven vessel; shall keep out of the way; right - power-driven vessel.

A vessel engaged in underwater operations.

The term "sailing vessel" means any vessel under sail provided that propelling machinery, if fitted, is not being used.

Two vessels: left - "I intend to overtake you on your starboard side"; right - "Yes ( _ . _ . )" or indicate such doubt by giving at least five short and rapid blasts on the whistle or flashes. 

Aground.