Learning how to use 得 to mean "must" must be done by those wishing to master Chinese!

Structure
Normally when you see 得 it's a particle and is pronounced "de". However, it can also be an auxiliary verb. In this case it's pronounced děi and means "must".

Examples

Shíjiān bù zǎo le, wǒ dé huí jiā le.
时间 不早了，我 得 回 家 了。
It's getting late.I have to go home.