An Acting rank is a military designation allowing a commissioned - or non-commissioned officer to assume a rank—usually higher and usually temporary—with the pay and allowances appropriate to that grade. As such, an officer may be ordered back to the previous grade. This situation may arise when a lower-ranking officer is called upon to replace a senior officer, or fill a position higher than the current rank held.

When addressing an individual with an acting rank, the person should be addressed as if the full rank was held. For example, a member who is an acting master seaman would be addressed as "Master Seaman Smith", and not "Acting Master Seaman Smith" since the "acting" is a designation, regardless of the individual's actual rank and clerical designation. It should also be noted that an exception is the rank of acting sub-lieutenant: they should be addressed verbally as mentioned ("sub lieutenant"), but in written documents should have their full, unedited title of "acting sub lieutenant."

Acting is the work of an actor or actress, which is a person in theatre, television, film, or any other storytelling medium who tells the story by portraying a character and, usually, speaking or singing the written text or play.

Most early sources in the West that examine the art of acting (Greek: ὑπόκρισις, hypokrisis) discuss it as part of rhetoric.

One of the first actors is believed to be an ancient Greek called Thespis of Icaria. An apocryphal story says that Thespis stepped out of the dithyrambic chorus and spoke to them as a separate character. Before Thespis, the chorus narrated (for example, "Dionysus did this, Dionysus said that"). When Thespis stepped out from the chorus, he spoke as if he was the character (for example, "I am Dionysus. I did this"). From Thespis' name derives the word thespian.

Acting requires a wide range of skills, including vocal projection, clarity of speech, physical expressivity, emotional facility, a well-developed imagination, and the ability to interpret drama. Acting also often demands an ability to employ dialects, accents and body language, improvisation, observation and emulation, mime, and stage combat. Many actors train at length in special programs or colleges to develop these skills, and today the vast majority of professional actors have undergone extensive training. Even though one actor may have years of training, they always strive for more lessons; the cinematic and theatrical world is always changing and because of this, the actor must stay as up to date as possible. Actors and actresses will often have many instructors and teachers for a full range of training involving, but not limited to, singing, scene-work, monologue techniques, audition techniques and partner work.

Rank refers to the relative position, value, worth, complexity, power, importance, authority, level etc. of a person or object, including: