How to use at, on and in correctly all the time
The three of them are prepositions of time and of place. A preposition is a small word that usually comes before a noun. It indicates the relationship between a noun and the other words of a sentence. There are many prepositions, but we will only look at three of them here, to see how they're used to talk about time and place.
The order in which they appear in the word "melatonin" is the right one, the one you should remember them by, which is why it is important not to forget the word "melatonin". Here's how this works.