What is the interpretation of "indeed, some assumption is sin," and what is the difference between doubt (shakk) and assumption (dhann)?

Allah Almighty forbids entertaining ill suspicions about believers. Not every suspicion is a sin. The forbidden suspicion refers to baseless accusation.

The forbidden suspicion means accusing people of evil without evidence, and it may lead to spying to confirm this accusation.

The term "suspicion" (الظن) is used for multiple meanings: certainty, predominant assumption, weak assumption, or doubt where probabilities are equal. The meaning is understood from the context.