What literary term is used in this sentence The youth ran like a madman?

The literary term used in the sentence "The youth ran like a madman" is simile.

Here's why:

* Simile: A simile is a figure of speech that compares two things using the words "like" or "as".

* In the sentence: The youth's running is being compared to the way a madman would run, using the word "like".

Therefore, the sentence uses a simile to create a vivid image of the youth's frantic speed.