我不知道玛丽是你的姐姐。

I had no idea that Mary was your sister.

Source: Tatoeba

Sentence Composition

1 我不知道 wǒbùzhīdào I don't know.
2 玛丽 Mǎlì
  1. Mary or Marie (name)
  2. Mali
=3 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)
=3 是 shì variant of 是 shì
=4 你 nǐ you (informal, as opposed to courteous 您 nín)
=4 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.)
5 的姐 dījiě female taxi driver
6 姐 jiě older sister