Word: 掉 (diào) to lose; to go missing; to shed (hair)

今天我的笔记本掉了。

Jīntiān wǒ de bǐjìběn diào le.

I lost my notebook today.

他完全疯掉了。

Tā wánquán fēng diào le.

He's completely lost his mind.

他开始掉头发了。

Tā kāishǐ diào tóufa le.

He is beginning to lose his hair.

别太操心了，不然会掉头发的。

Bié tài cāoxīnle, bùrán huì diào tóufa de.

Don't worry too much, or you'll go bald.

我把钥匙掉了。

Wǒ bǎ yàoshi diào le.

I have lost the key.

我的外套掉了一颗纽扣。

Wǒ de wàitào diào le yì kē niǔkòu.

My coat has lost a button.

我的钢笔掉了。

Wǒ de gāngbǐ diào le.

I dropped my fountain pen.

我的铅笔掉了。

Wǒ de qiānbǐ diào le.

I've lost my pencil.

这支笔和我昨天掉的那支一样。

Zhè zhī bǐ hé wǒ zuótiān diào de nà zhī yíyàng.

This is the same pen that I lost yesterday.