Retired USN Surface Warfare Officer here.<p>The differentiation between rudder and engine is crucial. The Conning Officer, who gives orders to the helm at the direction of the Officer of the Deck, will call rudder orders as "left standard rudder" or "right full rudder".<p>Engine orders will be given in terms of "all engines ahead 1/3", "back 1/3" or "port engine ahead 1/3, starboard engine back 1/3" (to put a clockwise twist on when maneuvering). Frequently when on a great circle voyage, one may have the port shaft making turns for, e.g. 13kts, and the starboard shaft just trailing in the water, for fuel efficiency.<p>The crucial point here is that these order terms are like strong data types in code. We do not mix them. In a stressful situation, e.g. the Straits of Malacca, the last thing anyone needs is entropy from a terminology mix-up. Lives are literally at stake.<p>Bonus point: the port/starboard nomenclature is also applies to spatial locations off of the centerline. Compartments go, level, frame (bow to stern numbering), centerline position. e.g.<p>6 4 2 0 1 3 5<p>Thus, as a young lad at the end of the Cold War, working on Aegis in CG-57, my computer room was O1-138-0-C.<p>The centerline numbering is in accordance with PESO: Port: Even, Starboard: Odd.<p>To this day, I set up my cel phone headset IAW PESO, based upon the day of the month. Go, Navy.