自然语言理解是研究如何让电脑读懂人类语言的一门技术，是自然语言处理技术中最困难的一项。

1. What?：何谓理解？
2. How?：电脑如何能理解人类语言。
3. When?：电脑了解到何种程度才算理解。
4. Where?：自然语言如何转换成电脑可理解的结构，如何保存。
5. Why?：电脑真的能理解吗？为何能、为何不能。

Natural language understanding (NLU) is a subtopic of natural language processing in artificial intelligence that deals with machine reading comprehension. NLU is considered an AI-hard problem.

The process of disassembling and parsing input is more complex than the reverse process of assembling output in natural language generation because of the occurrence of unknown and unexpected features in the input and the need to determine the appropriate syntactic and semantic schemes to apply to it, factors which are pre-determined when outputting language.