The word "呼吁" (hūyù) is formed through the combination of two semantically similar characters, each contributing to the overall meaning of "to appeal" or "to call for." The first character, "呼" (hū), originally means "to exhale" or "to shout," conveying the act of giving voice. The second character, "吁" (yù), means "to sigh" or specifically "to appeal." When paired, they create a binome (a two-character compound) where both elements reinforce the concept of a vocal and earnest public plea or request, amplifying the sense of urgency and solemnity beyond what either character could express alone.