How do I say 'I don't understand'?

Chinese comprehension vocabulary is channel-specific — you must name how the understanding failed:

• 听不懂 — hearing problem. The words came in but didn’t parse. This is what language learners say most. The 不懂 is a result complement: “listen + not comprehend.”
• 看不懂 — reading problem. The characters are visible but meaning doesn’t form.
• 不明白 — logic/reason problem. You heard/read the words but the idea doesn’t make sense.

The result complement pattern (verb + 得/不 + complement) is one of the most useful grammatical structures in Chinese. It describes whether an action achieves its result: 听得懂 (can understand by listening), 听不懂 (can’t understand by listening), 看得见 (can see), 看不见 (can’t see).

For language learners, the survival sequence:

1. 不好意思，我听不太懂。(Sorry, I don’t really understand.)
2. 请说慢一点。(Please speak more slowly.)
3. 你会说英语吗？(Do you speak English?)

The 不太 before 懂 softens it: 听不太懂 = “I don’t quite catch it” — gentler than 听不懂 which is the blunt “I don’t understand.”