To shorten something means to make it smaller or less long.
We often use this word when talking about time or tasks. For instance, if your teacher asks you to shorten your presentation from 10 minutes to 5 minutes, they want you to get rid of some unnecessary points and focus on the main ideas. You might also try to shorten a boring task by finding an easier way to do it, like using a shortcut on your computer. If you're planning a trip, you can try to shorten the distance by taking a detour or choosing a more direct route.
How common is "shorten"?
Word shorten is considered uncommon in modern English. It has a balanced usage among all categories: speech, fiction, newspapers and academic texts.
Definitions
verb
(transitive) To make shorter; to abbreviate.
(intransitive) To become shorter.
(transitive) To make deficient (as to); to deprive (of).
(transitive) To make short or friable, as pastry, with butter, lard, etc.
(transitive) To reduce or diminish in amount, quantity, or extent; to lessen.
Example: to shorten an allowance of food
(baking, of pastries, transitive) To make crumbly.
(nautical, transitive) To take in the slack of (a rope).
(nautical, transitive) To reduce (sail) by taking it in.
(transitive, dated) to dress (a baby) in a short (rather than long) gown