bounces

Bounces refer to the rebound motion that occurs when an object strikes a surface and returns away from it. In everyday language, the term is also used metaphorically to describe abrupt reversals or failures to deliver in digital communication and data analysis. The specific meaning depends on the field, but the common theme is a post‑impact change of direction or a failed transmission following an initial contact.

In physics and materials science, a bounce is quantified by the coefficient of restitution, defined as the ratio of speeds after and before impact. Values range from 0 (perfectly inelastic, no rebound) to 1 (perfectly elastic). Factors include material stiffness, surface texture, impact velocity, and energy loss due to deformation, heat, and sound. The term is widely used for sports balls, bumper surfaces, and vehicle suspensions.

In email systems, a bounce occurs when a message cannot be delivered to the recipient. Bounces are categorized as hard bounces, permanent failures such as invalid addresses, and soft bounces, temporary issues like a full mailbox or server rejection. Managing bounces is important for mail deliverability and sender reputation, and lists are routinely cleaned to remove addresses that repeatedly bounce.

In web analytics, the bounce rate is the percentage of single-visit sessions in which a user leaves after viewing only one page. A high bounce rate can indicate issues with page relevance, load times, or user experience; a low rate may indicate engaging content or effective navigation. Bounce rate is influenced by traffic source, device, and user intent, and is commonly used alongside other metrics to assess site performance.