You can tell that a submarine can dive beneath the ocean's surface, something a conventional boat cannot accomplish, by using the prefix sub-, which signifies under, below, or less than.
A ship that is submerged is called a submarine.
Because the word pre- signifies before, you might conclude that routinely washing your hands helps ward off colds.
To prevent anything is to put an end to it before it occurs.
You can use the prefix pre- to determine the likelihood that you will read a preprint of a book before it is released.
Something that hasn't been published for public consumption yet is called a preprint.
Before deciding whether or not to buy premade food if you don't want to cook it yourself, the prefix pre- means before.
You've already had something premade ready for you.
