What term describes the right or left side of any formation as viewed by an element within that formation?

The term that describes the right or left side of any formation as viewed by an element within that formation is "flank." In military terminology, a flank refers specifically to the side of a unit or formation. Understanding this concept is crucial in drill and formations, as it helps in positioning and movements during exercises or inspections. The flanks are significant because they can influence how units interact with each other and how they respond to commands, particularly in maneuvers and strategies.

The other terms do not capture this definition accurately. "Guide" refers to a designated individual who leads or directs a formation, ensuring uniformity and proper alignment. "Head" pertains to the front or leading part of the formation. "Front," while also related to positioning, generally indicates the forward-facing side of a formation rather than the lateral aspects defined by the flanks.