CIE

Cie, often written as CIE, is an abbreviation that can refer to several different concepts depending on context and language. In French usage, it is an abbreviation of compagnie and is commonly found in the names of companies, theatres, or military units, where it functions much like Co. in English. It commonly appears with a period after the abbreviation in formal writing, though punctuation usage can vary by style guide.

The acronym CIE most widely refers to the International Commission on Illumination, or Commission Internationale de l'Éclairage. This international body was established in 1913 to advance research, standardization, and application of light and color. The CIE develops important colorimetric standards and color spaces, such as the CIE 1931 XYZ color space and the CIELAB and CIEXYZ models, and it issues guidelines used in lighting design, photography, and color science.

In education, CIE has been used as the abbreviation for Cambridge International Examinations, the international examination board associated with Cambridge Assessment International Education. It previously branded itself as CIE and offers qualifications including the Cambridge IGCSE and Cambridge International A-Levels; the organization has since adopted the CAIE branding, though historical materials still use CIE.

Other uses exist in various fields and languages, including organizational names and industry-specific abbreviations. Because Cie is not unique to a single entity, the intended meaning is typically clear only from the surrounding context.