Millimeter wave refers to electromagnetic waves with wavelengths ranging from 1 millimeter to 10 millimeters, corresponding to frequencies between 30 GHz and 300 GHz. This part of the electromagnetic spectrum is used in various applications, including wireless communication, radar systems, and medical imaging. Due to their high frequency, millimeter waves can carry large amounts of data, making them suitable for 5G technology. However, they have limited range and can be absorbed by rain and atmospheric gases, which can affect their performance in certain conditions.