What does the term "derailment" mean?

The term "derailment" refers specifically to the unintended departure of a train from its tracks. This definition encompasses situations where a train may lose its structural integrity and veer off the rails, which can occur due to various factors such as track defects, equipment failures, or external impacts. Understanding this concept is critical for those involved in train operations and safety management, as derailments can lead to significant consequences, including accidents, delays, and damage to equipment and infrastructure.

The other options describe different train-related scenarios but do not accurately capture the meaning of "derailment." For instance, removing a train from service is a maintenance or operational decision, not an event pertaining to train movement on tracks. Intentional movements of trains to different tracks are part of normal operations and do not describe an error or accident. Lastly, delays due to weather are operational disruptions but do not indicate any physical misalignment of the train relative to its tracks, and hence are not linked to derailments.