The Greek language has a historical record that dates back more than 3,400 years. It is a language developed in Greek territory, which belongs to the Indo-European branch, and which became the preferred writing system for much of the history of this nation. Its alphabet, created around the 9th century BC, consists of 24 letters and is presumed to be the most complete of the time; its use continues to this day, mainly as mathematical, physical, computer and even hierarchical signs.

The fourth in the established order of these signs is “Delta”, represented as Δ, in upper case, and δ, in lower case, with a value of 4 within the Greek numeral system. Like the other Greek letters, within the nomenclature of applied sciences and mathematics, it has a vital importance; It is generally used to refer to changes in the value of a variable, being massive or reduced depending on whether it is expressed in its uppercase or lowercase form, to the discriminants of a polynomial and the Laplacians.

However, today this symbol is also known for being one of the names given to a series of secret projects directed by the CIA, such as MKDELTA. Such work of the Central Intelligence Agency, had as its purpose the knowledge of the effects of certain chemical substances in the organism, becoming the successor of the well-known MKULTRA project. In addition, it is the name of a US special operations unit, called 1st Special Forces Operational Detachment-Delta (SFOD-D), better known as Delta Force or Delta Force.