When combined, 下午 (xiàwǔ) literally means “down from noon,” which is the perfect description for “afternoon.” Adding 好 (hǎo) turns it into a polite greeting: “Afternoon good,” or as we say in English, “Good afternoon.”
Using time-specific greetings like “下午好” is a common sign of politeness and social awareness in Chinese culture. While “你好” (nǐ hǎo) is a universal “hello,” taking a moment to use the correct greeting for the time of day shows a greater level of attentiveness and respect. In Western cultures, especially American culture, “Good afternoon” can sometimes sound quite formal and is often replaced by a simple “Hi” or “Hello” in most daily interactions. In China, while casual greetings are also common among friends, “下午好” strikes a perfect balance. It is not considered overly formal for daily use in situations like greeting a shopkeeper, a security guard, or a colleague you pass in the hall. It's a small but significant gesture that helps maintain a harmonious and respectful social atmosphere. It reflects a culture where acknowledging the specific context of an interaction, including the time of day, is valued.