Yes
Of course. Use this for an enthusiastic and confident 'yes'.
Okay / Alright. Used to agree to a suggestion, similar to saying 'okay' in English.
Of course / Certainly. A slightly more formal or emphatic way to say 'yes'.
-Do you want a coffee? -Yes, please.
-Are we going to the movies on Saturday? -Of course!
-Do you need help with that? -Yes, thank you.
-Can we talk tomorrow? -Okay.
'Sí' is universally understood and is the most direct translation of 'yes' in all Spanish-speaking countries.
While 'sí' is standard, 'vale' is extremely common for 'okay' or to agree to something. It's used constantly in everyday conversation.
'Dale' is a very popular and casual way to say 'okay', 'deal', or 'go for it' when agreeing to a plan.
'Bueno' is very common for 'okay.' You will also hear 'órale' as an informal, enthusiastic 'yes' or 'let's do it'.
In addition to 'sí' and 'claro', you'll often hear 'listo' (literally 'ready') used to mean 'okay' or 'got it' as a form of agreement.
Confusing 'sí' with 'si' — The accent mark is critical. 'Sí' (with an accent) means 'yes'. 'Si' (without an accent) means 'if'. They are not interchangeable. 'Sí, voy' is 'Yes, I'm going.' 'Si voy' is 'If I go.'
Only using 'sí' — While 'sí' is always correct, relying on it exclusively can sound robotic or blunt. Native speakers use alternatives like 'claro' (of course) and 'bueno' (okay) to add nuance and sound more natural in conversation.
Using 'sí' to answer the phone — In many parts of Latin America, especially Mexico, the standard way to answer the phone is 'Bueno?'. In other regions, people may say 'Aló?' or 'Diga?'. Answering with 'Sí?' is uncommon and can sound abrupt.