Usage of the character 是

friend or foe? (quote from 沙家浜 ( Shājiābāng)) (蔣／蒋 ( Jiǎng) here refers to Chiang Kai-shek 蔣介石／蒋介石 ( Jiǎng Jièshí) and 汪 ( Wāng) refers to Wang Jingwei 汪精衛／汪精卫 ( Wāng Jīngwèi))

jiāngháishìlǎodelà

姜还是老的辣

[薑還是老的辣]

ginger gets spicier as it gets older (idiom)
the older, the wiser

rénshìtiěfànshìgāng

人是铁饭是钢

[人是鐵飯是鋼]

one can't function properly on an empty stomach (idiom)
an empty sack cannot stand upright

shìfēizìyǒugōnglùn

是非自有公论

[是非自有公論]

to determine right and wrong based on public opinion (idiom)
Public opinion will judge what's right and wrong.

tuánjiéjiùshìlìliang

团结就是力量

[團結就是力量]

unity is strength (revolutionary slogan and popular song of 1943)

tīngjiànfēngjiùshìyǔ

听见风就是雨

[聽見風就是雨]

lit. on hearing wind, to say rain
to agree uncritically with whatever people say
to parrot other people's words
to chime in with others

dīngshìdīng,mǎoshìmǎo

丁是丁，卯是卯

[丁是丁，卯是卯]

lit. to keep ding (the fourth heavenly stem) distinct from mao (the fourth earthly branch) (idiom)
fig. meticulous
conscientious
unambiguous

tānlánshìwàn'èzhīyuán

贪婪是万恶之源

[貪婪是萬惡之源]

Greed is the root of all evil.

nüzǐwúcáibiànshìdé

女子无才便是德

[女子無才便是德]

a woman's virtue is to have no talent (idiom)

shíjiānshìbǎshāzhūdāo

时间是把杀猪刀

[時間是把殺豬刀]

lit. time is a butcher's knife
fig. time marches on, relentless and unforgiving
nothing gold can stay

dīngshìdīng,mǎoshìmǎo

钉是钉，铆是铆

[釘是釘，鉚是鉚]

lit. a nail is a nail and a rivet is a rivet (idiom)
fig. meticulous
conscientious
unambiguous

jiǎndàolánlǐjiùshìcài

捡到篮里就是菜

[撿到籃裡就是菜]

all is grist that comes to the mill (idiom)

wénzizàixiǎoyěshìròu

蚊子再小也是肉

[蚊子再小也是肉]

lit. even a mosquito, though tiny, provides some nourishment (idiom)
fig. it's better than nothing

bùshìyuānjiābùjùtóu

不是冤家不聚头

[不是冤家不聚頭]

destiny will make enemies meet (idiom)
(often said about lovers who have a disagreement)

shībàishìchénggōngzhīmǔ

失败是成功之母

[失敗是成功之母]

Failure is the mother of success.

shǒuxīnshǒubèidōushìròu

手心手背都是肉

[手心手背都是肉]

lit. both the palm and the back of the hand are made of flesh (idiom)
fig. to both be of equal importance
to value both equally

yīshìyī,èrshì'èr

一是一，二是二

[一是一，二是二]

lit. one is one, two is two (idiom)
fig. things are (or ought to be) perfectly clear-cut
unequivocal

xūyàoshìfāmíngzhīmǔ

需要是发明之母

[需要是發明之母]

Necessity is the mother of invention (European proverb).

wǔbǎiniánqiánshìyījiā

五百年前是一家

[五百年前是一家]

five hundred years ago we were the same family (idiom) (said of persons with the same surname)

shēntǐshìgémìngdeběnqián

身体是革命的本钱

[身體是革命的本錢]

lit. the body is the revolution's capital
fig. good health is a prerequisite for work (Mao Zedong's saying)

shìkěrěn,shúbùkěrěn

是可忍，孰不可忍

[是可忍，孰不可忍]

if this can be tolerated, what cannot? (idiom)
enough is enough

bùshìyúsǐjiùshìwǎngpò

不是鱼死就是网破

[不是魚死就是網破]

lit. either the fish dies or the net gets torn (idiom)
fig. it's a life-and-death struggle
it's either him or me

húlulǐmàideshìshénmeyào

葫芦里卖的是什么药

[葫蘆裡賣的是什麼藥]

what has (he) got up (his) sleeve?
what's going on?

kǔhǎiwúbiān,huítóushì'àn

苦海无边，回头是岸

[苦海無邊，回頭是岸]

The sea of bitterness has no bounds, turn your head to see the shore (idiom). Only Buddhist enlightenment can allow one to shed off the abyss of worldly suffering.
Repent and ye shall be saved!

fǎn Měishìgōngzuòfù Měishìshēnghuó

反美是工作赴美是生活

[反美是工作赴美是生活]

being anti-American is the job, but life is in America (jocular comment made about public figures who are brazenly xenophobic but whose family live abroad)

bùshìyījiārénbùjìnyījiāmén

不是一家人不进一家门

[不是一家人不進一家門]

people who don't belong together, don't get to live together (idiom)
marriages are predestined
people marry because they share common traits

kēxuéjìshùshìdìyīshēngchǎnlì

科学技术是第一生产力

[科學技術是第一生產力]

science and technology is the number one productive force (from a 1978 speech by Deng Xiaoping 鄧小平／邓小平 ( Dèng Xiǎopíng) introducing the Four Modernizations 四個現代化／四个现代化 (sìgexiàndàihuà))

shìluózishìmǎ,lāchūlailiùliu

是骡子是马，拉出来遛遛

[是騾子是馬，拉出來遛遛]

see 是騾子是馬，牽出來遛遛／是骡子是马，牵出来遛遛 (shìluózishìmǎ,qiānchūlailiùliu)

shìluózishìmǎ,qiānchūlailiùliu

是骡子是马，牵出来遛遛

[是騾子是馬，牽出來遛遛]

lit. to see whether it's a mule or a horse, take it out for a walk (idiom)
fig. the proof of the pudding is in the eating
to show what one is made of

shíjiànshìjiǎnyànzhēnlǐdewéiyībiāozhǔn

实践是检验真理的唯一标准

[實踐是檢驗真理的唯一標準]

Actual practice is the sole criterion for judging truth (item from Deng Xiaoping theory, from 1978)

céngjīngcānghǎinánwéishuǐ,chúquè Wū Shānbùshìyún

曾经沧海难为水，除却巫山不是云

[曾經滄海難為水，除卻巫山不是雲]

there are no rivers to one who has crossed the ocean, and no clouds to one who has passed Mount Wu (idiom)
one who has seen the world doesn't stop at small things

bùguǎnbáimāohēimāo,zhuōzhùlǎoshǔjiùshìhǎomāo

不管白猫黑猫，捉住老鼠就是好猫

[不管白貓黑貓，捉住老鼠就是好貓]

it doesn't matter whether a cat is white or black; as long as it catches mice it's a good cat (variant of a Sichuanese saying used in a speech by Deng Xiaoping 鄧小平／邓小平 ( Dèng Xiǎopíng) in 1962, usually associated with his economic reforms starting in 1978, in which pragmatism was favored over ideological purity)

qiánbùshìwànnéngde,méiqiánshìwànwànbùnéngde

钱不是万能的，没钱是万万不能的

[錢不是萬能的，沒錢是萬萬不能的]

money isn't everything, but without money you can do nothing (idiom)