Learn Hardcore Chinese: xièxie nǐ, wǒ yídìng qǐng nǐ chī wǎnfàn. - Thank you; I will definitely treat you to dinner.

They serve different roles. In 谢谢你, 你 is who you’re thanking. In 请你吃晚饭, 你 is the person you’re inviting/treating. You can drop 你 after 谢谢 in casual speech (谢谢，…), but you cannot drop the 你 after 请, because 请 needs a person as its object: 我一定请你吃晚饭 is correct; 我一定请吃晚饭 is not.

Can I just say 谢谢 instead of 谢谢你?

Yes. 谢谢 is perfectly natural and slightly less personal. 谢谢你 is more directed and warm. For extra politeness or gratitude, you can say 谢谢您 (formal/respectful) or 太谢谢你了 / 非常感谢你 (stronger thanks).

What exactly does 请 mean here? Is it the same as English “please”?

Here 请 means “to invite/treat (and pay).” In 请你吃晚饭, it implies “I’ll host and cover the bill.” Chinese 请 can also mean “please” in set phrases like 请进 (please come in), 请坐 (please sit), but you cannot use 请 as a universal “please” the way English does.

Why do we need 吃 before 晚饭? Can I say 请你晚饭?

You need the verb of consumption: 请你吃晚饭 (“treat you to eat dinner”). Saying 请你晚饭 is ungrammatical. Similarly: 请你喝咖啡 (treat you to coffee), 请你看电影 (treat you to a movie).

Is 请你吃饭 also okay? What’s the difference from 请你吃晚饭?

Yes. 请你吃饭 is more general (“treat you to a meal”); the time is unspecified. 请你吃晚饭 specifies dinner. You can also say 请你吃午饭 (lunch).

What is the grammar pattern of 我一定请你吃晚饭?

It’s a serial-verb (pivotal) construction: 我 (subject) + 一定 (adverb) + 请 (verb “invite”) + 你 (object of 请) + 吃 (second verb) + 晚饭 (object of 吃). In English terms: “I [definitely] [invite you] [to eat dinner].”

What does 一定 add? Does it mean “must”?

一定 here means “definitely/certainly (for sure).” It conveys the speaker’s firm intention or promise, not external obligation. For obligation, Chinese prefers 必须 or 得. Compare:

我会请你吃晚饭 = I will (likely) treat you.
我一定请你吃晚饭 = I will definitely treat you (promise).
我一定会请你吃晚饭 = even stronger emphasis.

Where does 一定 go? Can I put it at the end?

Place 一定 before the verb phrase: 我一定请你…. Don’t put it at the end: × 我请你吃晚饭，一定 is ungrammatical in this meaning. For strong reassurance, sentence-final 的 works: 我一定请你吃晚饭的 (I definitely will, for sure).

Do I need 会 to express the future?

No. Chinese doesn’t require a future tense marker. Context and adverbs like 一定 already indicate futurity. 我一定请你吃晚饭 is fine without 会. Adding 会 just adds a shade of “will/likely.”

Would adding 吧 change the tone?

Yes. 吧 softens it into a suggestion/invitation: 谢谢你，我请你吃晚饭吧 (“How about I treat you to dinner?”). Without 吧, it sounds like a firm promise/commitment.

Can/should I add 了 anywhere?

Not in the promise clause. 我一定请你吃晚饭了 is odd. But you CAN use 了 after thanks for emphasis: 太谢谢你了 (“Thank you so much!”). That 了 marks exclamatory tone/change of state.

Pronunciation: how do I say 谢谢你 naturally?

Say xièxie nǐ, with the second 谢 in a neutral tone (轻声). In natural speech, 你 can also be light: xièxie ni. So you’ll often hear 4th tone + neutral, plus a light “ni.”

Why is 一定 written as yídìng and not yīdìng?

Tone sandhi: 一 changes to second tone (yí) when followed by a fourth tone (定). So 一定 is pronounced yídìng.

Any tone sandhi in 请你?

Yes. 请 (qǐng, 3rd tone) before 你 (nǐ, 3rd tone) becomes 2–3 due to third-tone sandhi. So you pronounce it roughly qíng nǐ (2–3).

Are there measure words for meals here, like 顿/餐?

You can say 请你吃顿饭 (very natural, “treat you to a (one) meal”). For dinner, 请你吃晚饭 is most common. 请你吃顿晚饭 exists but is less common. Avoid 请你吃一个晚饭; 个 works in 吃个饭 (colloquial), but with 晚饭 people usually don’t use 个.

Is 请你吃晚饭 understood as “I pay,” or just “let’s have dinner”?

It strongly implies “I’ll treat/pay.” If you just want to suggest dining together without the treating nuance, say 一起吃晚饭吧 or 我们去吃晚饭吧. To emphasize paying, you can also say 我请客 (“It’s my treat.”).

How to make this more polite/formal?

Use 您 for respect: 谢谢您，我一定请您吃晚饭。 Add softeners/time words: 改天/找个时间/有空的时候我请您吃个饭。 Formal register prefers 晚餐: 请您吃晚餐.

Can I say 请你来吃晚饭? Does it change the meaning?

Yes. 请你来吃晚饭 explicitly invites the person to come (to your place or a venue you designate). 请你吃晚饭 focuses on the treating; the location is unspecified. Both imply you’re hosting.