Lie/Lay
You lie down to go to bed. Chickens lay eggs. If you wish to be obtuse, you can say you're going to lay yourself down. That the eggs are lying in the nest. But lay is a transitive verb (i.e., it takes an object, i.e., it is enacted upon something else), and lie is an intransitive verb (i.e. is does not take an object, i.e. it cannot be enacted upon something else).
Lie also means to tell an untruth, a source of some confusion, I suppose, when people think it only means to tell an untruth.
Bonus points: I lie down every night, just like I lay down last night; indeed I have lain down in a similar manner ever since I can remember. When will that chicken lay her egg? She laid an egg yesterday. She has lain an egg every day for the past two years, why not today?
Haha, exercises in conjugation.