When combined, 明白 (míngbai) literally means “bright and clear,” which is a wonderful metaphor for the feeling of understanding something. Therefore, adding 不 (bù) at the beginning creates 不明白 (bù míngbai), or “not bright and clear” in your mind—you don't understand.
While “不明白” is a straightforward phrase, its usage can touch on the cultural concept of “face” (面子, miànzi). In most daily situations, especially for a language learner, saying “我不明白” is perfectly acceptable and even expected. It shows you are engaged and want to learn. However, in more formal or hierarchical settings (e.g., a junior employee speaking to a high-level boss), directly saying “我不明白” might sometimes be perceived as slightly blunt. It could subtly imply that the speaker's explanation was not good. In these situations, a person might use a softer, more indirect approach to save face for both parties, such as: “不好意思，我没太听懂，您能再解释一下吗？” (Bù hǎoyìsi, wǒ méi tài tīng dǒng, nín néng zài jiěshì yīxià ma?) - “Excuse me, I didn't quite catch that, could you explain it again?” This contrasts with Western, low-context cultures where saying “I don't get it” or “I don't understand” is almost always seen as a neutral request for information, with little to no bearing on the speaker's status or the relationship. For a learner, though, “不明白” is a safe and reliable choice.
“不明白” is used constantly in all aspects of modern life.
The most common point of confusion for learners is the difference between 不明白 (bù míngbai) and 不懂 (bù dǒng). While they both translate to “don't understand,” they have different connotations.
Common Mistake: Using “不明白” for a lack of skill.
In short: Use 不明白 when you need clarification on something said or done. Use 不懂 when you lack the underlying knowledge about a whole topic. When in doubt as a beginner, 不明白 is often a safer and more polite choice.