The word "寰宇" is formed by combining the characters "寰" and "宇", each contributing related meanings. "寰" includes the radical "宀" for dwelling or space, with "睘" suggesting vastness, often referring to the world. "宇" also uses "宀" for space, with "于" as a phonetic component, originally meaning eaves but extended to signify the cosmos. Together, they form a compound where both characters semantically reinforce the concept of the entire world or universe.