What is the abbreviation for kilohertz?

The correct abbreviation for kilohertz is 'kHz'. According to standard International System of Units (SI) rules, the prefix 'kilo' (meaning one thousand) is always represented by a lowercase 'k'. Additionally, because the unit 'Hertz' is named after the physicist Heinrich Hertz, the first letter of its abbreviation must be capitalized ('H'), followed by a lowercase 'z'. Putting the prefix and unit together correctly gives you 'kHz', making all other capitalization variants incorrect.