| A path through which electricity flows before returning to its source. | |
| In a transmission, where all gears are constantly in contact and turning with one another. | |
| Exhaust gas recirculation system. | |
| A signal that varies the ratio of on-time to off-time, resulting in a square wave that can range between zero and 100; in a process, the ratio of on-time to total cycle time; in fuel injectors, the percentage on-time to total cycle time; in solenoids, the percentage of on-time to total cycle time. |