Good night is 晚安 (wǎn ān) in Mandarin Chinese. 晚(wǎn) means late. The character is made up of the radical “日(rì) ”(sun) on the left and“免(Miǎn)”(to avoid)on the right.安(ān)means to be peaceful or safe, it consists of the radical “宀”on top and “女”(female) on lower. The upper “宀”symbols a house,the below “女”represents a girl. In shape “安”looks like a girl under a house roof safely.
People like to say 再见 (zàijiàn)or 拜拜 (bàibài)in Chinese language after conversation, if it is late at night,people love to say 晚安 either.

A:Good night!晚安!
B:Good night!Go to bed early, have a sleep night!
Wǎn’ān! Zǎodiǎn shuì, zhù nǐ hǎo mèng!
晚安! 早点 睡, 祝你 好梦!

A:Good night!晚安!
B:See you tomorrow!
Míngtiān jiàn!
明天 见!

Frequently-used words and phrases:

睡觉 (shuìjiào) is “to sleep”in Chinese
洗脸 (xǐliǎn) is “to wash face”in Chinese
刷牙 (shuāyá)is “to brush your teeth”in Chinese
洗脚 (xǐ jiǎo) is “to wash feet”in Chinese