Level 3 · Intermediate
Mistakenly think: 以为
Subj. + 以为 + Clause (that turned out wrong) · Traditional: Subj. + 以為 + Clause (that turned out wrong)
以为 (yǐwéi) means "thought (wrongly)". The moment you say 我以为你不来了 "I thought you weren't coming", everyone hears the second half: …but here you are. It's the word for beliefs that reality has already corrected, so it pairs naturally with 其实 "actually".
For opinions you still hold, use 觉得 or the more formal 认为: 我觉得这本书很有意思 "I think this book is interesting". Swap in 以为 there and you'd be announcing that you no longer think so.
Examples
我以为你不来了。
我以為你不來了。
wǒ yǐ wéi nǐ bù lái le
I thought you weren't coming.
我以为今天是星期六，其实是星期五。
我以為今天是星期六，其實是星期五。
wǒ yǐ wéi jīn tiān shì xīng qī liù qí shí shì xīng qī wǔ
I thought today was Saturday — actually it's Friday.
他以为我是中国人。
他以為我是中國人。
tā yǐ wéi wǒ shì zhōng guó rén
He (mistakenly) thought I was Chinese.
我觉得这本书很有意思。
我覺得這本書很有意思。
wǒ jué de zhè běn shū hěn yǒu yì si
I think this book is really interesting.
Common mistakes
✗ 我以为中文很有意思，所以每天都学。
✓ 我觉得中文很有意思，所以每天都学。
以为 signals your thought was WRONG — an opinion you still hold takes 觉得 or 认为.
Related grammar points
See it in a story
Read this pattern in context: Dotting the Dragon's Eyes — free graded stories with tap-to-reveal pinyin and translations.
