Cool MateHave no idea vs Not sure
When to use each in English, with meaning, register, and examples.
Have no idea
InformalTop 2,000 (common)
Not sure
| Have no idea | Not sure | |
|---|---|---|
| Pronunciation | 🇬🇧 //hæv nō aɪˈdɪə//🇺🇸 //hæv noʊ aɪˈdiə// | |
| Meaning | Not know something at all | |
| Example | I have no idea where my keys went. | - |
| Register | Informal | - |
| How common | Top 2,000 (common) | - |
| Collocations | have no idea about, have no idea how, have no idea where | - |
| Common mistakes | Confused with 'have an idea' - means the opposite., Used too formally - mostly informal., Omitting 'no' - 'have idea' is incorrect. | - |
| Usage notes | Used mainly in casual conversations. It may not be suitable for formal writing or speech. | - |
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Frequently asked questions: Have no idea vs Not sure
What's the difference between Have no idea and Not sure?
Have no idea: Not know something at all Not sure:
Can I use Have no idea and Not sure interchangeably?
Not always. Have no idea and Not sure are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.