| 独一无二 | dú yī wú èr | unique and unmatched (idiom); unrivalled; nothing compares with it |
一不做，
二不休 | yī bù zuò ,
èr bù xiū | don't do it, or don't rest (idiom); either give up, or go through to the end; Since we started, we must carry it through whatever happens.; in for a penny, in for a pound |
| 一二八事变 | yī èr bā shì biàn | Shanghai incident of 28th January 1932, Chinese uprising against Japanese quarters of Shanghai |
| 一来二去 | yī lái èr qù | gradually; little by little; in the course of time |
一回生，
二回熟 | yī huí shēng ,
èr huí shú | lit. at first raw, later ripe (idiom); unfamiliar at first but you get used to it; strangers at first meeting, but soon friends; awkward at first but becoming skillful later; an acquired taste |
| 一氧化二氮 | yī yǎng huà èr dàn | nitrous oxide N2O; laughing gas |
| 一清二白 | yī qīng èr bái | perfectly clean; blameless; unimpeachable (idiom) |
| 一退六二五 | yī tuì liù èr wǔ | lit. 1 divided by 16 is 0.0625 (abacus rule); fig. to deny responsibility; to pass the buck; also written 一推六二五 |
| 丁二醇 | dīng èr chún | butyl glycol |
| 三分之二 | sān fēn zhī èr | two-thirds |
| 三十二位元 | sān shí èr wèi yuán | 32-bit (computing) |
| 三心二意 | sān xīn èr yì | in two minds about sth (idiom); half-hearted; shilly-shallying |
| 上海第二医科大学 | Shàng hǎi Dì èr Yī kē Dà xué | Shanghai Second Medical University |
| 不二价 | bù èr jià | one price for all; fixed price |
| 不二法门 | bù èr fǎ mén | the one and only way; the only proper course to take |
| 不管三七二十一 | bù guǎn sān qī èr shí yī | regardless of the consequences; recklessly relying on a hopelessly optimistic forecast |
| 丙二醇 | bǐng èr chún | propylene glycol; propane-1,2-diol C3H6(OH)2 |
| 幺二 | yāo èr | one-two or ace-deuce (smallest throw at dice); a prostitute |
| 九牛二虎之力 | jiǔ niú èr hǔ zhī lì | tremendous strength (idiom) |
| 二一添作五 | èr yī tiān zuò wǔ | lit. one half equals zero point five (division rule in abacus reckoning); to share fairly between two parties; to go fifty-fifty |
| 二丁醚 | èr dīng mí | dibutyl ether |
| 二七区 | Èr qī qū | Erqi district of Zhengzhou city 郑州市, Henan |
| 二世 | èr shì | the Second (of numbered Kings); second generation (e.g. Chinese Americans), Japanese nissei |
| 二人世界 | èr rén shì jiè | world with only two people (usually refers to a romantic couple); romantic couple's world |
| 二代 | èr dài | secondary; twice in the year (of generations of insects, harvests etc) |
| 二伏 | èr fú | same as 中伏, last ten days of July and first ten days of August, the second of 三伏 sān fú, three hottest periods of the year |
| 二侧 | èr cè | two sides |
| 二价 | èr jià | negotiable price |
| 二元醇 | èr yuán chún | ethyl alcohol C2H5OH |
| 二分 | èr fēn | second part; the equinox |
| 二分之一 | èr fēn zhī yī | one half |
| 二分裂 | èr fēn liè | binary division (in bacterial reproduction) |
| 二分音符 | èr fēn yīn fú | minim (music) |
| 二分点 | èr fēn diǎn | the two equinoxes |
| 二十 | èr shí | twenty; 20 |
| 二十一世纪 | èr shí yī shì jì | 21st century |
| 二十一点 | èr shí yī diǎn | blackjack (card game) |
| 二十七号 | èr shí qī hào | 27th day of a month |
| 二十世纪 | èr shí shì jì | 20th century |
| 二十二号 | èr shí èr hào | 22nd day of a month |
| 二十五史 | èr shí wǔ shǐ | twenty four dynastic histories (or 25 or 26 in modern editions) |
| 二十八宿 | èr shí bā xiù | the twenty-eight constellations |
| 二十八号 | èr shí bā hào | 28th day of the month |
| 二十六岁 | èr shí liù suì | 26 years old |
| 二十六号 | èr shí liù hào | 26th day of a month |
| 二十四节气 | èr shí sì jié qi | the 24 solar terms, calculated from the position of the sun on the ecliptic, that divide the year into 24 equal periods |
| 二十四号 | èr shí sì hào | 24th day of a month |
| 二十多 | èr shí duō | over 20 |
二十年目睹之怪现
状 | èr shí nián mù dǔ zhī guài xiàn zhuàng | The strange state of the world witnessed over 20 years, novel by late Qing novelist Wu Jianren 吳趼人, classified as "novel of denunciation" 谴责小说 |
| 二十面体 | èr shí miàn tǐ | icosahedron |
