There are quite a few different words in Mandarin that are often translated as 'improve' in English. Here's a guide to five of the most common ones, and the differences between them.
提高: to increase
提高 is literally 'raise high', and expresses improving something by taking it to a higher level. It's often used with rates, quantities and measurements etc.
Common collocations for 提高:
水平 (shuǐpíng) : level
率 (lǜ) : rate
Wèile tígāo wǒ de hànyǔ shuǐpíng, wǒ xiǎng qù zhōngguó xuéxí.
"I'd like to study in China to improve the level of my Chinese."
Wǒmen bàgōng zhī suǒyǐ shì yīnwèi gōngsī méiyǒu tígāo wǒmen de gōngzī.
"The reason we're on strike is that the company hasn't improved our wages."
Zhège yàopǐn huì tígāo bìngrén de cúnhuó lǜ.
"This drug will improve the survival rates of patients."
改进: to make progress (with something)
改进 is improve in the direct, obvious sense of making something better. 改 means 'to change', and 进 means 'to advance' or 'to make progress'. It's about improving the quality or fitness of something.
Common collocations for 改进:
做法 (zuòfǎ) : method
态度 (tàidu) : attitude
行为 (xíngwéi) : behaviour
Yàoshi nǐ xiǎng pīpíng biérén dehuà, shǒuxiān xūyào gǎijìn zìjǐ de zuòfǎ.
"If you want to criticise other people, first you must improve your own methods."
Wǒ xīwàng gǎijìn zìjǐ de gōngzuò tàidù.
"I hope to improve my attitude to work."
Wèile gǎijìn xuéshēng de xuéxí tàidù, xuéxiào ràng tāmen wǎn yīgè xiǎoshí lái shàngkè.
"In order to improve the students' attitude to their studies, the school let them start class an hour later."
改善: to make something good
改善 is similar to 改进, except it implies more strongly that the thing to be improved is currently lacking or deficient in some way. Again, 改 is 'to change', and 善 is 'good', so 改善 is literally 'to change something and make it good'.
Common collocations for 改善:
环境 (huánjìng) : environment
情况 (qíngkuàng) : situation
关系 (guānxì) : relations
问题 (wèntí) : problem
Zhège zhèngcè de mùbiāo shì gǎishàn zuì pínkùn de shìchǎng de huánjìng.
"The aim of this policy is to improve the environment in the poorest cities."
Tā rènwéi tàijí quán gǎishàn le tā de shēnghuó.
"He believes that Tai Ji has improved his life."
Yīngguó bìxū gǎishàn zìjǐ de huǒchē wǎng zhuàng xìtǒng wèntí.
"The UK must improve the problems with its rail network."
改良: to reform
改良 is similar to 改善, but is rarer and more formal (an equivalent in English might be 'to ameliorate'). Like 善, 良 means 'good', so 改良 could also be seen as 'to change something and make it good'. 改良 is part of the word 改良主义 – 'reformism', as opposed to favouring a rapid revolution.
Common collocations for 改良:
结构 (jiégòu) : structure
技术 (jìshù) : technique
土地 (tǔdì) : territory
工业 (gōngyè) : industry
Jīnglǐ dǎsuàn gǎiliáng gōngsī de jiégòu.
"The manager wants to improve the company's structuring."
Tōngguò yíchuán xiūshì, wǒmen kěyǐ gǎiliáng nóngzuòwù.
"Through genetic modification, we can improve crops."
Zhège xīn de shìchǎng kěnéng gǎiliáng quánbù de gōngyè.
"This new market may improve the entire industry."
进步 is commonly a noun, meaning 'improvement' or 'progress'. 进 also appears in 改进, above, and means 'progress', whilst 步 is 'step' or 'stage'. 进步 can also be a verb, but doesn't take an object.
Jīntiān wǒmen qǔdé le hěnduō jìnbù.
"We've made a lot of improvements today."
Bù zhīdào yào děng duō cháng shíjiān, wǒ de chuàngzuò nénglì cái néng jìnbù.
"I don't know how long I'll have to wait before my creative ability improves."