# 信誓旦旦

xìn shì dàn dàn

Make emphatic, solemn assurances

## Meaning & wording

**Literally:** Pledges declared with firm sincerity

**Register:** Standard · expressive

[People & connection](https://chinese-idioms.yudis.dev/idioms/topics/relationships)

## When to use it

Describe confident promises, often later questioned.

Does not guarantee the promise is true.

## Understanding the expression

The speaker offers a promise with such certainty that hesitation seems absent. The expression can record sincere commitment, but often appears before a contrast: someone promised firmly and later failed to deliver. It describes the form and force of the assurance rather than proving reliability. Concrete terms and subsequent actions make a promise credible. The grandest declaration may matter less than a modest commitment that someone consistently keeps.

## Examples

他信誓旦旦地保证准时交货。

### Traditional Chinese

他信誓旦旦地保證準時交貨。

tā xìn shì dàn dàn dì bǎo zhèng zhǔn shí jiāo huò 。

He solemnly guaranteed delivery on time.

她信誓旦旦，却又失约。

### Traditional Chinese

她信誓旦旦，卻又失約。

tā xìn shì dàn dàn ， què yòu shī yuē 。

She made firm promises but broke them again.

销售员信誓旦旦地说没有额外费用。

### Traditional Chinese

銷售員信誓旦旦地說沒有額外費用。

xiāo shòu yuán xìn shì dàn dàn dì shuō méi yǒu é wài fèi yòng 。

The salesperson emphatically assured us there were no additional charges.

他不再信誓旦旦，只按时完成任务。

### Traditional Chinese

他不再信誓旦旦，只按時完成任務。

tā bú zài xìn shì dàn dàn ， zhī àn shí wán chéng rèn wu 。

He stopped making grand assurances and simply completed tasks on time.

## Sources & reference checks

Original explanations and examples from Chinese Idioms Almanac. Source-checked October 6, 2026.

- [CC-CEDICT · forms & pronunciation](https://www.mdbg.net/chinese/dictionary?page=worddict&wdqb=%E4%BF%A1%E8%AA%93%E6%97%A6%E6%97%A6)

- [Ministry of Education · 成語典](https://dict.idioms.moe.edu.tw/idiomView.jsp?ID=879&webMd=1&la=0)

## Keep exploring

- [心心相印 xīn xīn xiāng yìn Understand one another deeply ](https://chinese-idioms.yudis.dev/idioms/xin-xin-xiang-yin)

- [心悦诚服 xīn yuè chéng fú Accept willingly and sincerely ](https://chinese-idioms.yudis.dev/idioms/xin-yue-cheng-fu)

- [心照不宣 xīn zhào bù xuān Understand each other without saying it ](https://chinese-idioms.yudis.dev/idioms/xin-zhao-bu-xuan)

- [心直口快 xīn zhí kǒu kuài Speak frankly and readily ](https://chinese-idioms.yudis.dev/idioms/xin-zhi-kou-kuai)

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