If something was originally a certain way, or "should be" a certain way, the Chinese words used are often "本来" (běnlái) and "原来" (yuánlái). "本来" (běnlái) is usually an adverb while "原来" (yuánlái) could be either an adjective or adverb. However, they are used in different ways and different circumstances, so this article will help you distinguish when and where to use them.
"本来" as an adverb often requires "就" for emphasis
Subject + 本来 + 就 + 很/不 + Adj
Subject + 本来 + 就 + 会/要/得/应该+ Verb
chuàng yè běn lái jiù bú róng yì.
It's not supposed to be an easy thing to start your own business.
zhào gù hái zi běn lái jiù shì fù mǔ de zé rèn.
Taking care of children is supposed to be the responsibility of parents.
lǎo shī běn lái jiù yīng gāi hǎo hǎo bèi kè.
Teachers are supposed to prepare their lessons well.
měi guó rén běn lái jiù huì shuō liú lì de yīng wén.
Americans are supposed to speak fluent English.
If something happened unexpectedly later, "本来" is preferred rather than "原来" considering there is a change of the original situation. Since it has happened, the structure "是···的" is suggested here. If you are just trying to give some fact, then "是···的" is optional.
Subject + 本来 + 是 +（不）要/会/得/应该 + Verb + 的，但是/可是/不过/现在/后来···
wǒ běn lái shì yào qù cān jiā nǐ de shēng rì pài duì de, kě shì zhōu mò tū rán yào jiā bān.
I was going to go to your birthday party, but I had to work some extra time this weekend.
tā běn lái shì yīng gāi kǎo dé gèng hǎo de, kě shì nà tiān tā fā gāo shāo le.
He would have done better on the test, but he had a high fever that day.
wǒ běn lái shì yào gēn tā jié hūn de, kě shì hòu lái fā xiàn le wǒ men zhēn de bú hé shì.
I was originally going to marry him, but then I found that we are just not meant for each other.
If you've got an opinion to express after stating how it "should be," then "本来+就" will help you sound more convincing.
Subject + 本来 + 就 + [what you think it is true or right]
nǐ běn lái jiù gòu shòu le, hái yào jiǎn féi ma?
You are already thin enough and you still want to lose weight?
tā jiǎng dé běn lái jiù bú duì, wéi shén me hái yào wǒ tīng tā de?
What he said was wrong all along, so why do you still want me to listen to what he says?
tā běn lái jiù bú shì gè hǎo rén, nǐ zěn me hái yào bāng tā?
He was never a good person. Why do you still want to help him?
tā běn lái jiù bú xǐ huān nǐ, nǐ bié zài zhuī tā le.
She never liked you in the first place, so stop going after her.
"原来" is more used to emphasize what you accidentally find out or realize in some certain situation. It's similar to "as it turns out…". For this usage, "原来" is normally located at the beginning or the middle of the sentence.
"原来"更多是用于强调在某种情况下你意外发现或意识到什么。它类似于"as it turns out…"，这个用法里，"原来"一般放于句首或句子中间。
The most two useful structures are as follows:
原来 + 是（因为/为了）+ [fact/truth/reason/purpose]
怪不得 + [observation]，原来 + [reason]
yuán lái shì nǐ a! wǒ gāng cái zhēn méi kàn chū lái.
It is you! I didn't recognize you until just now.
yuán lái shì zhè yàng a, nà shì wǒ zuò cuò le.
Oh, that's it. I was doing it wrong all along.
guài bú dé nǐ zhōng wén shuō dé zhè me hǎo, yuán lái nǐ zài zhōng guó zhù le sān shí duō nián.
No wonder your Chinese is so good. You lived in China for more than 30 years.
guài bú dé zǒng shì duì tā nà me hǎo, yuán lái nǐ yī zhí dōu xǐ huān tā.
No wonder you treat him so well. You've had feelings for him the whole time.
"原来" is also used as an adjective, meaning "previous" or "former".
zhè shì wǒ yuán lái de jiā.
This is my old house.
tā yuán lái de gōng sī guān mén le.
His former company closed down.
nǐ men yuán lái de kàn fǎ bú shì zhè yàng de.
This is not how you previously thought about it.
nǐ yuán lái de tóu fā nà me hēi, xiàn zài bái le hěn duō.
Your hair was so black before, but now it's become a lot whiter.
Translated from: AllSetLearning
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