I Don't Know
A slightly stronger, very common way to say 'I have no idea.'
Use this to say 'I'm not sure.' Use 'seguro' if you are male and 'segura' if you are female.
A rhetorical question meaning 'Who knows?' Used informally when the answer is unknown to everyone.
What time does the bus arrive? —I don't know.
Where did Ana buy her cell phone? —I have no idea.
Is it going to rain tomorrow? —I'm not sure, but the sky is gray.
Why is the store closed? —Who knows?
The phrase 'No sé' is universal and understood everywhere in the Spanish-speaking world. It's the most standard and reliable option.
In very informal contexts, you might hear 'Sepa,' which is a slangy shorthand for 'Quién sabe' or 'Sepa Dios' (God knows).
Besides 'No sé' and 'Ni idea,' it's common to hear '¿Qué sé yo?' which translates to 'What do I know?' It's used similarly to the English expression.
'Ni idea' (No idea) is extremely common in casual conversation, often used interchangeably with 'No tengo idea.'
The phrase 'No sé' is used exactly as it is in Latin America. 'Ni idea' is also very common slang.
Using 'Yo no sé' all the time. The 'yo' (I) is usually dropped in Spanish because the verb 'sé' already means 'I know.' Saying 'No sé' is more natural. Use 'Yo no sé' only for strong emphasis.
Confusing 'saber' and 'conocer.' Use 'No sé' for facts or information (e.g., 'No sé la hora'). Use 'No conozco' for people or places (e.g., 'No conozco a Juan'). Saying 'No conozco la respuesta' is a common mistake.
Using the wrong verb form, like 'No sabe.' This means 'He/She doesn't know' or 'You (formal) don't know.' The correct form for 'I' is 'sé,' so you must say 'No sé.'