Meaning of kǔ:
苦
bitter
Zhè bēi kāfēi yǒudiǎn kǔ.
这杯咖啡有点苦。
This cup of coffee is a bit bitter.
hardship; pain
Tā jīnglìle hěn duō kǔ nàn, dàn zuìzhōng chénggōngle.
他经历了很多苦难,但最终成功了。
He went through a lot of hardships but eventually succeeded.
Tā gǎndào hěn kǔ, yīnwèi tā de chǒngwù shēngbìng le.
他感到很苦,因为他的宠物生病了。
He is feeling a lot of pain because his pet is sick.
to suffer; to bring suffering to
Tā jīnglìle hěnduō kǔnàn.
他经历了很多苦难。
He has gone through a lot of hardship.
Tā de shēnghuó hěn kǔ.
他的生活很苦。
His life is very difficult.
painstakingly
Tā měitiān dōu zài wèile mèngxiǎng ér kǔ liàn.
他每天都在为了梦想而苦练。
He practices painstakingly every day for his dream.