The difference between 苦 and 努力
The words 苦 and 努力 are similar in meaning, but they are often used differently.
The adverb 苦
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 .
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 .Examples
我苦学了四年，终于大学毕业了
I had studied hard for four years and finally graduated from university
wǒ kǔxué le sì nián, zhōngyú dàxué bìyè le
他们苦练了三个月，这次比赛的成绩比上次好多了
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
大家苦想了半天，可是没有一个人想出办法来
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.
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.
Examples
他为了赚钱而努力工作
He works hard to make money
tā wèi le zhuàn qián ér nǔlì gōngzuò
学生应该努力学习
Students should study hard
xuéshēng yīnggāi nǔlì xuéxí
As an adjective
As an adjective, 努力 has the meaning “persistent”, ”diligent”.
Examples
她工作比他努力
She works harder than him
tā gōngzuò bǐ tā nǔlì
她特别努力
She is very hardworking
tā tèbié nǔlì
As a verb
As a verb, 努力 has the meaning “to try”, “to make an effort”.
Examples
我们会努力的
We will do our best
wǒmen huì nǔlì de
你要努力才能成功
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”.
Examples
我为他的努力感到自豪
I am proud of his persistence
wǒ wèi tā de nǔlì gǎndào zìháo
他们的努力都付诸东流
Their efforts were in vain
tāmen de nǔlì dōu fùzhūdōngliú