| 二里头 | Èr lǐ tou | Erlitou (Xia dynasty 夏朝 archaeological site at Yanshi 偃师 in Luoyang 洛阳, Henan) |
| 二重 | èr chóng | double; repeated twice |
| 二重下标 | èr chóng xià biāo | double subscript; doubly indexed |
| 二重唱 | èr chóng chàng | duet |
| 二重奏 | èr chóng zòu | duet (in music) |
| 二重根 | èr chóng gēn | a double root of an equation |
| 二重母音 | èr chóng mǔ yīn | diphthong |
| 二阿姨 | èr ā yí | auntie, second eldest of sisters in mother's family |
| 二阶 | èr jiē | second order; quadratic (math.) |
| 二项式系数 | èr xiàng shì xì shù | a binomial coefficient (math.); the number of combinations |
| 二项式定理 | èr xiàng shì dìng lǐ | the Binomial Theorem (math.) |
| 二头肌 | èr tóu jī | biceps muscle |
| 二鬼子 | èr guǐ zi | traitor; collaborator with the enemy |
| 二黄 | èr huáng | one of the two chief types of music in Chinese opera; Peking opera; also written 二簧; see also 西皮 |
| 五氧化二钒 | wǔ yǎng huà èr fán | Vanadium pentoxide V2O5; vanadic anhydride |
| 京二胡 | jīng èr hú | Jing'erhu, a two-stringed fiddle intermediate in size and pitch between the Jinghu 京胡 and Erhu 二胡, used to accompany Chinese opera; also called 京胡 |
| 依地酸二钴 | yī dì suān èr gǔ | kelocyanor |
| 备用二级头呼吸器 | bèi yòng èr jí tóu hū xī qì | backup regulator; octopus (diving) |
| 光二极管 | guāng èr jí guǎn | photodiode; light-emitting diode (LED) |
| 八二三炮战 | bā èr sān pào zhàn | bombardment of Kinmen by PRC forces that started August 23rd 1958, also called second Taiwan strait crisis |
| 六・二五战争 | liù · èr wǔ zhàn zhēng | the Korean war (started June 25 1950) |
| 六二五事变 | liù èr wǔ shì biàn | Korean war (dating from North Korean invasion on 25th Jun 1950) |
| 划一不二 | huà yī bù èr | fixed; unalterable |
| 包二奶 | bāo èr nǎi | to cohabit with and financially support a mistress |
| 十二 | shí èr | twelve; 12 |
| 十二分之一 | shí èr fēn zhī yī | one twelfth |
| 十二地支 | shí èr dì zhī | the 12 earthly branches 子, 丑, 寅, 卯, 辰, 巳, 午, 未, 申, 酉, 戌, 亥 (used cyclically in the calendar and as ordinal numbers) |
| 十二宫 | shí èr gōng | the twelve equatorial constellations or signs of the zodiac in Western astronomy and astrology, namely: Aries 白羊, Taurus 金牛, Gemini 双子, Cancer 巨蟹, Leo 狮子, Virgo 室女[Shi4 nu:3], Libra 天秤, Scorpio 天蝎, Sagittarius 人马, Capricorn 摩羯, Aquarius 宝瓶, Pisces 双鱼 |
| 十二支 | shí èr zhī | the 12 earthly branches 子, 丑, 寅, 卯, 辰, 巳, 午, 未, 申, 酉, 戌, 亥 (used cyclically in the calendar and as ordinal number) |
| 十二星座 | shí èr xīng zuò | the twelve constellations on the ecliptic plane; the signs of the zodiac |
| 十二时辰 | shí èr shí chen | twelve divisions of the day of early Chinese and Babylonian time-keeping and astronomy |
| 十二月份 | shí èr yuè fèn | December |
| 十二码 | shí èr mǎ | 12-yard (sports); penalty kick |
| 十二经 | shí èr jīng | twelve channels of traditional Chinese medicine |
| 十二经脉 | shí èr jīng mài | twelve channels of traditional Chinese medicine |
| 十二角形 | shí èr jiǎo xíng | dodecagon |
| 十二边形 | shí èr biān xíng | dodecagon |
| 十二面体 | shí èr miàn tǐ | dodecahedron |
| 南门二 | Nán mén èr | Alpha Centauri or Rigel Kentaurus |
只知其一，
不知其二 | zhǐ zhī qí yī ,
bù zhī qí èr | to know the first, but not know the second (idiom); only partial information |
| 四一二 | sì yī èr | 12th April; refers to Chiang Kai-shek's coup of 12th April 1927 against the communists in Shanghai |
| 四一二事变 | sì yī èr shì biàn | the coup of 12th Mar 1927, an attempt by Chiang Kai-shek to suppress the communists; called 反革命政變 or 惨案 in PRC literature |
| 四一二反革命政变 | sì yī èr fǎn gé mìng zhèng biàn | counterrevolutionary coup of 12th April 1927, Chiang Kai-shek's coup against the communists in Shanghai |
| 四一二惨案 | sì yī èr cǎn àn | the massacre of 12th Mar 1927; the Shanghai coup of 12th Mar 1927 by Chiang Kai-shek against the communists |
| 四十二章经 | sì shí èr zhāng jīng | The Sutra in Forty-two Sections Spoken by the Buddha, the first Chinese Buddhist text, translated in 67 by Kasyapa-Matanga 迦葉摩騰 and Gobharana 竺法蘭 (Dharmaraksha) |
| 土卫二 | Tǔ wèi èr | Enceladus (moon of Saturn) |
| 大二 | dà èr | second-year university student |
| 大浦洞二 | Dà pǔ dòng èr | Taepodong 2, North Korean rocket |
| 大浦洞二号 | Dà pǔ dòng èr hào | Taepodong 2, North Korean rocket |
| 天冬苯丙二肽酯 | tiān dōng běn bǐng èr tài zhǐ | aspartame C14H18N2O (artificial sweetener) |
