Millihertz (mHz) refers to a unit of frequency equal to one thousandth of a hertz. It's commonly used for measuring small and low frequencies in various fields such as electronics, physics, and medicine. Some synonyms for the word millihertz include kilomillihertz, microhertz, and nanohertz. Kilomillihertz (kHz) is equivalent to one thousand millihertz, while microhertz (µHz) is one-thousandth of a millihertz. Nanohertz (nHz), on the other hand, is one billionth of a hertz. Other related terms that can be associated with millihertz include amplitude, wavelength, and period, among others. Understanding these terms is crucial in various fields where accurate frequency measurements are essential.