Subject + 看见 + (了) + Object
看见 (kànjiàn) is a verb meaning "to see" or "to catch sight of." It is a resultative complement compound where 看 means "to look" and 见 indicates the successful result of seeing. Use 看见 to emphasize that someone actually saw something, as opposed to 看 alone which just means "to look."
我在地铁上看见了一个老同学。
Wǒ zài dìtiě shàng kànjiàn le yí gè lǎo tóngxué.
I saw an old classmate on the subway.
你看见我的钥匙了吗?我找了半天。
Nǐ kànjiàn wǒ de yàoshi le ma? Wǒ zhǎo le bàntiān.
Have you seen my keys? I've been looking for ages.
她一抬头就看见窗外在下雪。
Tā yì táitóu jiù kànjiàn chuāng wài zài xià xuě.
As soon as she looked up, she saw it was snowing outside the window.