cannot avoid or help doing something
必須，不得不
they must needs depart.
他們不得不離開(kāi)。
it is or was necessary or unavoidable
必須，不得不
if needs must, they will eat any food.
如果必須的話，他們什么食物都要吃。
(proverb)sometimes you have to do something you would rather not
(諺)情勢(shì)所迫，只得如此