The word 期间 is formed through the logical combination of two meaningful characters: 期, which carries the core idea of a fixed or designated period of time (like a term, phase, or deadline), and 间, which denotes an interval, space, or span within defined boundaries. When fused, 间 acts to specify and interiorize the concept presented by 期; it essentially focuses on the internal duration or the "within-the-boundaries" span of that designated timeframe. Thus, the compound conceptually marks the interior expanse of a given period, resulting in the meaning of "during the time of" or "in the course of".