Most people do not confuse these two verbs, but their similarity deserves a blog post.

Problem:
These two verbs are spelled so similarly that there definitely is potential to treat them as synonyms, which they are not.

Explanation:
This verb “persecute” dates back to the first half of the fifteenth century.

“Persecute” begins with the prefix “per”, which means utterly or thoroughly.

The other part of “persecute” is related to the word “sequence”, a definition of which is something that follows.

Knowing these roots, it is easy to understand how the verb “persecute” means to pursue persistently with oppressive or harassing treatment.

The verb “prosecute” dates back to 1432 but apparently did not get applied as a legal term until 1579.

“Prosecute” begins with the prefix “pro”, which in this verb means favor for some party.

As with “persecute”, the other part of “persecute” is related to the word “sequence”, a definition of which is something that follows.

Knowing these roots, one can understand how the verb “prosecute” means to seek to enforce or carry on.

Solution:
Think harassment when you see the verb “persecute”; think legal proceeding when you see the verb “prosecute”.