A convenient summary of the many “Yes’s” in Vietnamese:
- Có
- Okay
-
Đúng rồi - that’s right
-
Vâng (ạ) - show respect to superior/elderly
-
Dạ (vâng) - show respect to superior/elderly or customer service
And then, there are some cases where a Yes/No question should not be answered in a typical Yes/No way if you want to sound more natural. For example, “Anh có bút CHƯA? Do you have a pen YET?” - “Rồi. Already (for Yes)” or “Chưa. Not yet (for No)”. It’s a high-contextual language
Hope this helps