| 四氢大麻酚 | sì qīng dà má fēn | Tetrahydrocannabinol, THC |
| 四氯乙烯 | sì lǜ yǐ xī | tetrachloroethylene |
| 四海升平 | sì hǎi shēng píng | lit. all four oceans are peaceful; worldwide peace (idiom) |
| 四海为家 | sì hǎi wéi jiā | to regard the four corners of the world all as home (idiom); to feel at home anywhere; to roam about unconstrained; to consider the entire country, or world, to be one's own |
| 四海皆准 | sì hǎi jiē zhǔn | appropriate to any place and any time (idiom); universally applicable; a panacea |
| 四海飘零 | sì hǎi piāo líng | drifting aimlessly all over the place (idiom) |
| 四清 | sì qīng | see 四清运动; the “Four Clean-ups” Movement |
| 四清运动 | sì qīng yùn dòng | the “Four Clean-ups” Movement (1963-66), a nationwide movement to clean things up in the fields of politics, economy, organization and ideology (historical) |
| 四湖 | Sì hú | Si or Ssuhu township in Yunlin county 云林县, Taiwan |
| 四湖乡 | Sì hú xiāng | Si or Ssuhu township in Yunlin county 云林县, Taiwan |
| 四溅 | sì jiàn | (foam flying) in all directions |
| 四物汤 | sì wù tāng | four-substance decoction (si wu tang), tonic formula used in Chinese medicine |
| 四环素 | sì huán sù | tetracycline |
| 四碳糖 | sì tàn táng | tetrose (CH20)4, monosaccharide with four carbon atoms |
| 四级 | sì jí | grade 4; fourth class; category D |
| 四级士官 | sì jí shì guān | sergeant first class |
| 四维 | sì wéi | the four social bonds: propriety, justice, integrity and honour; see 礼义廉耻; the four directions; the four limbs (Chinese medicine); four-dimensional |
| 四维时空 | sì wéi shí kōng | four dimensional space-time (in relativity) |
| 四维空间 | sì wéi kōng jiān | four dimensional space (math.) |
| 四圣谛 | sì shèng dì | the Four Noble Truths (Buddhism); see also 四谛 and 苦集灭道 |
| 四脚朝天 | sì jiǎo cháo tiān | four legs facing the sky (idiom); flat on one's back |
| 四脚蛇 | sì jiǎo shé | lizard; common spoken equivalent of 蜥蜴 |
| 四旧 | sì jiù | the Four Olds (target of the Cultural Revolution) |
| 四号电池 | sì hào diàn chí | AAA battery (Taiwan); PRC equivalent: 七号电池 |
| 四角形 | sì jiǎo xíng | square; quadrilateral |
| 四角柱体 | sì jiǎo zhù tǐ | cuboid; rectangular prism (math.) |
| 四角号码 | sì jiǎo hào mǎ | four corner code (input method for Chinese characters) |
| 四角裤 | sì jiǎo kù | boxer shorts |
| 四谛 | sì dì | the Four Noble Truths (Budd.), covered by the acronym 苦集滅道: all life is suffering 苦, the cause of suffering is desire 集, emancipation comes only by eliminating passions 灭, the way 道 to emancipation is the Eight-fold Noble Way 八正道 |
| 四轮马车 | sì lún mǎ chē | chariot |
| 四轮驱动 | sì lún qū dòng | four wheel drive |
| 四近 | sì jìn | nearby |
| 四郊 | sì jiāo | suburb; outskirts (of town) |
| 四部曲 | sì bù qǔ | tetralogy |
| 四重奏 | sì chóng zòu | quartet (musical ensemble) |
| 四门轿车 | sì mén jiào chē | sedan (motor car) |
| 四灵 | sì líng | four divinities; four divine emperors; four mythical creatures symbolic of propsperity and longevity, namely phoenix 凤, turtle 龟, dragon 龙, Chinese unicorn 麒麟; also 四象, the four division of the sky |
| 四面楚歌 | sì miàn chǔ gē | lit. on all sides, the songs of Chu (idiom); fig. surrounded by enemies, isolated and without help |
| 四头肌 | sì tóu jī | quadriceps muscle group; thigh muscles |
| 四体 | sì tǐ | one's four limbs; two arms and two legs |
四体不勤，
五谷不分 | sì tǐ bù qín ,
wǔ gǔ bù fēn | never move your four limbs, can't distinguish the five crops (idiom); living as a parasite |
