我起初以為他是你弟弟。

At first, I thought he was your brother.

Source: Tatoeba

Sentence Composition

1 我 wǒ
  1. I
  2. me
  3. my
2 起初 qǐchū originally; at first; at the outset
3 以為 yǐwéi to think; to believe (often with the implication that the belief is mistaken – unless referring to one's own current belief)
4 他 tā
  1. (third-person singular) (since the early 20th century, usu. male) he; him; his
  2. (bound form) other; another; some other (as in 他日 tārì and 他人 tārén)
=5 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=5 是 shì variant of 是 shì
=6 你 nǐ you (informal, as opposed to courteous 您 nín)
=6 你 nǐ you (Note: In Taiwan, 妳 is used to address females, but in mainland China, it is not commonly used. Instead, 你 is used to address both males and females.)
7 弟弟 dìdi younger brother

classifiers: 個, 位