What is the abbreviation for megahertz?

The unit 'hertz' is named in honor of the physicist Heinrich Hertz, so its abbreviation requires a capital 'H' and a lowercase 'z' (Hz). The metric prefix 'mega' means one million and is always represented by a capital 'M'. Combining these rules gives us 'MHz' as the correct abbreviation for megahertz. The other options are incorrect because they either use a lowercase 'm' (which stands for milli, or one-thousandth) or a lowercase 'h' (which violates the capitalization rule for units derived from a person's name). Capitalization is strictly standardized in electronic units to avoid massive scaling errors, such as confusing millihertz (mHz) with megahertz (MHz).