Final answer:
The T wave on an ECG represents ventricular repolarization, marking the transition back to a polarized (relaxed) state before the next cardiac cycle.
Step-by-step explanation:
As the ventricles return to their polarized state, the T wave is recorded on an electrocardiogram (ECG). During a cardiac cycle, after the ventricles have contracted, they must repolarize before they can contract again. The T wave on an ECG signifies this ventricular repolarization and it is followed by ventricular diastole, where the heart muscles relax. This is crucial for the health and function of the heart, indicating that the ventricles are ready for the next beat.