chứ

The particle chứ is highly frequent in everyday spoken Vietnamese. It serves several primary functions depending on the sentence type and position:

• In questions (Tag Question): It translates to "..., right?" or "..., surely?". Unlike neutral yes-no questions, using chứ means you already expect the answer to be "yes" or agreeable. It can also be used in rhetorical questions to express disbelief. The phrase chứ gì is also heavily used as a tag question meaning "..., right?" or "..., I bet?" to point out the obvious or make a presumption.
• In statements/answers (Emphatic Affirmation): It translates to "Of course!" or "Certainly!". It asserts certainty, states the obvious, or pushes back against someone's doubt. Common fixed phrases include chứ sao, chứ gì, chứ sao nữa, and chứ còn gì nữa. These are frequently used as standalone responses meaning "of course!" or "obviously!".
• In commands (Urging or Coaxing): It can add force, urgency, or impatience to a command, translating to "come on" or "do it already!". However, it is also frequently used to soften a blunt order into a friendly, encouraging request (e.g., Học bài đi chứ! - Come on, study!).
• At the beginning of a sentence (Pivoting/Following up): It translates to "Then..." or "What about...?" when shifting the topic or following up on a previous statement (e.g., Chứ anh thì sao? - Then what about you?).

Nuance and Register:
Chứ is highly assertive and inherently a conversational particle. While the final particle is completely natural in spoken Vietnamese, it is generally avoided in formal written texts. In polite spoken contexts, simply follow it with a polite address pronoun or the respect particle (e.g., chứ ạ). In Southern dialects, it is often pronounced and written as chớ. However, be careful not to confuse this Southern pronunciation with the standard negative command don't (a formal synonym for don't).

Note: Do not confuse this with the softer particle isn't it? (used for musing) or the neutral tag right?. Also, be aware that chứ can function as a mid-sentence conjunction meaning "but", "rather", or "instead". This conjunction is perfectly acceptable and highly common in formal written Vietnamese, and is most frequently paired with negative words like không or không phải (e.g., Tôi uống trà chứ không uống cà phê - I drink tea rather than coffee), which is distinct from its use as a final particle.