Lock = 锁 [Suǒ]

A hand holds a smartphone, and a chain runs from the phone to a cuff around the wrist. The two are locked together: 锁.

锁 (suǒ) means “lock,” and also “to lock.” The left side, 钅, is the metal radical.

To lock the door is 锁门 (suǒ mén). A key is 钥匙 (yàoshi), and a phone’s lock screen is 锁屏 (suǒpíng).

出门别忘了锁门。 — Chūmén bié wàng le suǒ mén. — Don’t forget to lock the door when you go out.

我的手机锁屏了。 — Wǒ de shǒujī suǒpíng le. — My phone screen is locked.