When referring to the smallest unit of measurement or analysis, "elementary unit" may be substituted with various synonyms. The term "basic unit" can be used to describe the fundamental building block of a structure or system. "Fundamental unit" pertains to the elemental principles that govern the system. "Smallest unit" signifies the minimum size required for a single entity, while "atomic unit" highlights the indivisibility of the basic unit. "Elemental building block" emphasizes the components that form the foundation of the system in question. Regardless of which synonym is used, each connotes the concept of a fundamental unit being the key building block in a larger structure or system.