The word **再三** is formed as an **adverbial compound** by combining two synonymous or reinforcing numerals to express the concept of repetition and insistence. The character **再** means "again" or "once more," while **三** means "three." In classical Chinese, numerals were often used not for literal counting but to indicate frequency or multiplicity. Thus, the combination **再三** leverages the reduplicative and emphatic nature of both characters to create an idiomatic meaning of "repeatedly," "over and over," or "time and again," emphasizing persistent action rather than a literal "two and three" times.