2. Unit of measurement: K stands for thousands, that is, 1000. For example: km (kilometers, kilometers), kg (kiloram, kilograms), kB (kilobytes, kilobytes) and so on.
3. Gold jewelry industry: it means gold content, which is called "golden position". The gold content per carat (abbreviation of karat in English, German and French, often written as K) is 4. 166%,18k =18 * 4.166%.
4. Physics: indicates the bulk elastic modulus; Represents absolute zero-273.16℃; Represents the Boltzmann constant: k =1.3806505 (24) ×10-23j/k, or the spring constant of Hooke's law; That is, the electrostatic constant k = 9.0×10.9 nm 2/c 2.