| 四 | sì | four; 4 |
| 四人帮 | sì rén bāng | Gang of Four: Jiang Qing 江青, Zhang Chunqiao 張春橋, Yao Wenyuan 姚文元, Wang Hongwen 王洪文, who served as scapegoats for the excesses of the cultural revolution |
| 四边形 | sì biān xíng | quadrilateral |
| 四川 | Sì chuān | Sichuan province (Szechuan) in southwest China, abbr. 川 or 蜀, capital Chengdu 成都 |
| 四个现代化 | sì gè xiàn dài huà | Deng Xiaoping's four modernizations practiced from the 1980s (possibly planned together with Zhou Enlai), namely: modernization of industry, agriculture, national defense and science and technology; abbr. to 四化 |
| 四周 | sì zhōu | all around |
| 四方 | sì fāng | four-way; four-sided |
| 四面体 | sì miàn tǐ | tetrahedron |
| 四大 | sì dà | the four elements: earth, water, fire, and wind (Buddhism); the four freedoms: speaking out freely, airing views fully, holding great debates, and writing big-character posters, 大鸣大放, 大辩论, 大字报 (PRC) |
| 四面 | sì miàn | all sides |
| 四季 | sì jì | four seasons, namely: spring 春, summer 夏, autumn 秋 and winter 冬 |
| 四处 | sì chù | all over the place; everywhere and all directions |
| 四肢 | sì zhī | the four limbs of the body |
| 四时 | sì shí | the four seasons, namely: spring 春, summer 夏, autumn 秋 and winter 冬 |
| 四角 | sì jiǎo | the four corners (of a rectangle); the eaves that the four corners of a building |
| 四面八方 | sì miàn bā fāng | in all directions; all around; far and near |
| 四边 | sì biān | four sides |
| 四国 | Sì guó | Shikoku (one of the four main islands of Japan) |
| 四化 | sì huà | abbr. for Deng Xiaoping's four modernizations 四个现代化 |
| 四平 | Sì píng | Siping prefecture level city in Jilin province 吉林省 in northeast China |
| 四声 | sì shēng | the four tones of classical Chinese phonetics, namely: level or even tone 平声, third tone 上声, fourth tone 去声, entering tone 入声; the four tones of modern standard Chinese pronunciation, namely: First or high level tone 阴平声, Second or rising tone 阳平声, Third or low-falling-raising tone 上声, Fourth or falling tone 去声 |
| 四象 | sì xiàng | four divisions (of the twenty-eight constellations 二十八宿 of the sky into groups of seven mansions), namely: Azure Dragon 青龙, White Tiger 白虎, Vermilion Bird 朱雀, Black Tortoise 玄武 |
| 四氯化碳 | sì lǜ huà tàn | carbon tatrachloride |
| 四川省 | Sì chuān shěng | Sichuan province (Szechuan) in southwest China, abbr. 川 or 蜀, capital Chengdu 成都 |
| 四起 | sì qǐ | to spring up everywhere; from all around |
| 四舍五入 | sì shě wǔ rù | to round up to the nearest integer; to discard four, but treat five as whole (of decimal points) |
| 四分音符 | sì fēn yīn fú | crotchet (music) |
| 四书 | Sì shū | Four Books, namely: the Great Learning 大学, the Doctrine of the Mean 中庸, the Analects of Confucius 论语, and Mencius 孟子 |
| 四分五裂 | sì fēn wǔ liè | all split up and in pieces (idiom); disunity (in an organization); complete lack of unity; to disintegrate; falling apart; to be at sixes and sevens |
| 四围 | sì wéi | all around; on all sides; encircled |
| 四邻 | sì lín | one's nearest neighbors |
| 四旁 | sì páng | nearby regions |
| 四散 | sì sàn | to disperse; to scatter in all directions |
| 四川盆地 | Sì chuān pén dì | Sichuan basin |
| 四通八达 | sì tōng bā dá | roads open in all directions (idiom); accessible from all sides |
| 四顾 | sì gù | to look around |
| 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 |
| 四下 | sì xià | everywhere |
| 四下里 | sì xià li | all around |
| 四世同堂 | sì shì tóng táng | four generations under one roof (idiom); Four Generations under One Roof, novel by Lao She 老舍 |
| 四乙基铅中毒 | sì yǐ jī qiān zhōng dú | tetraethyl lead poisoning |
| 四元数 | sì yuán shù | quaternion (math) |
| 四分之一 | sì fēn zhī yī | one-quarter |
| 四分之三 | sì fēn zhī sān | three quarters |
| 四分卫 | sì fēn wèi | quarterback (QB) (American football) |
| 四十 | sì shí | forty; 40 |
| 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) |
