Here's a breakdown:
* "Im-" prefix: This prefix generally indicates a negative or opposite meaning. It often comes from Latin and French roots. It's common in words where the root word begins with a consonant, like "impolite" (polite), "impossible" (possible), "impatient" (patient), etc.
* "Un-" prefix: This prefix also indicates a negative or opposite meaning. It's generally used when the root word begins with a vowel, like "unhappy" (happy), "unaware" (aware), "uneasy" (easy), etc.
However, there are some exceptions to this general rule:
* "Un-" before "p": While the "im-" prefix is more common before "p," the "un-" prefix is not entirely unheard of. You might find words like "unprofessional" or "unpleasant" in use, though they are often considered less formal or more informal than their "im-" counterparts.
* "In-" before "p": In some cases, the "in-" prefix is also used before "p," like in "inpatient" (a patient staying in a hospital). This prefix is more common for words with Latin origins.
Why "Impolite" and "Impatient" are Preferred:
Over time, these words have become standardized with the "im-" prefix. They are more commonly used and recognized, and using the "un-" prefix might sound strange or unfamiliar to many native English speakers.
Ultimately, while both "unpolite" and "unpatient" are technically grammatically correct, they are less common and less widely accepted than "impolite" and "impatient."