The adverb 苦 is used to emphasize that a person spends a lot of energy doing something.
This adverb is placed before a one-syllable verb that indicates an action requiring mental and physical effort.
For example: 学 , 劝 , 干 .
I had studied hard for four years and finally graduated from university
wǒ kǔxué le sì nián, zhōngyú dàxué bìyè le
They had trained hard for three months, and the results of this competition were much better than last time
tāmen kǔliàn le sān ge yuè, zhè cì bǐsài de chéngjì bǐ shàng cì hǎo duō le
Everyone thought hard for a long time but couldn’t come up with a solution.
dàjiā kǔxiǎng le bàntiān, kěshì méi yǒu yí ge rén xiǎngchū bànfǎ lái
The word 努力
努力 can be an adverb, a verb, a noun or an adjective.
As an adverb
As an adverb, 努力 has the meaning “diligently”, “hard”.
The adverb is placed before a verb.
He works hard to make money
tā wèi le zhuàn qián ér nǔlì gōngzuò
Students should study hard
xuéshēng yīnggāi nǔlì xuéxí
As an adjective
As an adjective, 努力 has the meaning “persistent”, ”diligent”.
She works harder than him
tā gōngzuò bǐ tā nǔlì
She is very hardworking
tā tèbié nǔlì
As a verb
As a verb, 努力 has the meaning “to try”, “to make an effort”.
We will do our best
wǒmen huì nǔlì de
You have to work hard to succeed
nǐ yào nǔlì cái néng chénggōng
As a noun
As a noun, 努力 has the meaning “diligence”, “persistence”.