Promilletta

Promilletta is a term with no official status in metrology. It is a neologism that sometimes appears in informal discussions about measurement scales or in speculative fiction. The word blends promille (per thousand) with the diminutive suffix -etta, suggesting a smaller subunit.

Proposed interpretation: in a hypothetical usage, one promilletta could be defined as one-thousandth of a promille, i.e., one part per million of the base quantity (1/1,000,000). Under this reading, 5 promille would be 0.5%, while 1 promilletta would be 0.000001 of the base. Because there is no widely accepted standard, other interpretations may be found, including treating promilletta as a purely didactic or fictional unit without fixed magnitude.

Usage and status: promilletta is not included in the International System of Units (SI) or any recognized national standard. It is rarely used in formal scientific communication, and when encountered it should be treated as a defined term within a specific text, with explicit equivalence stated to avoid ambiguity.

See also: promille, parts per million (ppm), per mille, metrology, units of measurement, diminutives in Romance languages.