Delta wave
![This is a screen shot of a patient during Slow Wave Sleep (stage 3). The high amplitude EEG is highlighted in red. This screen shot represents a 30-second epoch (30 seconds of data).](/Images/godic/202501/08/Sleep_EEG_Stage_43116.jpg")
A delta wave is a high amplitude brain wave with a frequency of oscillation between 0–4 hertz. Delta waves, like other brain waves, are recorded with an electroencephalogram (EEG) and are usually associated with the deep stage 3 of NREM sleep, also known as slow-wave sleep (SWS), and aid in characterizing the depth of sleep.