How is begging the question related to circular reasoning?

In the study of logic, the terms "begging the question" and "circular reasoning" are closely related, though they are sometimes distinguished by their structure.

"Begging the question" is the informal English equivalent of the Latin term petitio principii ("an assumption at the outset"). It describes a logical fallacy where a premise explicitly or implicitly assumes the truth of the conclusion rather than providing independent support for it.1

Circular reasoning, or circulus in probando ("circle in proving"), is often considered a specific form of petitio principii. While some use the terms interchangeably, circular reasoning is frequently defined as a chain of two or more arguments where the conclusion is eventually used to support the initial premise.1

In essence, both fallacies fail the test of good reasoning because they rely on the assumption that the conclusion is already true. While "begging the question" often refers to a basic premise-conclusion pair, circular reasoning typically involves a more extended, cyclical structure of inference.1