What is the abbreviation for kilohertz?

The correct abbreviation for kilohertz is 'kHz'. In the International System of Units (SI), strict capitalization rules apply to both prefixes and base units. The prefix 'kilo' stands for one thousand and is always designated with a lowercase 'k'. The unit 'hertz' is named after the physicist Heinrich Hertz. Because it is derived from a person's proper name, its symbol is capitalized, making it 'Hz'. When you combine the lowercase prefix and the capitalized unit symbol, you get 'kHz'. Options like 'KHZ' or 'khz' are incorrect because they fail to follow standard SI capitalization rules.