Reliability (R): The probability an item will perform its intended function with no failure for a given time interval and under given conditions (e.g., environment and loads). Other words, the probability an item will be in and remain in an uptime state.

Maintainability (M): The probability a failed item will be restored or repaired to a specified condition within a given time interval. Other words, the probability a failed item (an item in a downtime state) will be returned to an uptime state within a given time interval.

Availability (A): The probability a repairable item item will perform its intended function at a given point or interval of time when operated and maintained in a prescribed manner. Other words, the probability a repairable item will be in an uptime state and will recover from downtime states. A mathematical function of Reliability and Maintainability (R&M).

Risk: Potential loss or potential gain. The uncertain deviation (delta) in the execution of a management plan: Actual results = Planned results +/- Risk.

Ideally from an RMA Plan, the RMA team performs three major functions, namely, (1) Design for RMA, (2) RMA verification, and (3) Analytical physics. For specific RMA tasks click here.