Sievertide

The sievertide is a unit used in theoretical discussions of radiobiology and in some science fiction contexts to quantify the pace of radiation-induced biological damage. It is not an established SI unit and has no official recognition by bodies such as the International System of Units or the ICRP. The name is a portmanteau of sievert and the suffix -ide, signaling a derived, time-aware measure that combines dose with a temporal dimension to reflect how damage accumulates and repair processes unfold over time.

In proposed definitions, one sievertide represents a unit of cumulative biological effect equivalent to the damage produced by a dose of one sievert delivered to a reference tissue within a specified time window, accounting for dose rate and repair processes. Because the exact time window and tissue factors vary by definition, sievertide values are not directly comparable across models. The unit is intended to facilitate discussion of dose-rate effects and time-dependent repair, rather than to replace established dosimetric quantities.

Applications and status: The sievertide appears mainly in theoretical papers, modeling exercises, and speculative fiction. It has limited practical use because there is no consensus standard, and because established measures such as the gray, sievert, and dose-rate concepts already capture dose, energy deposition, and biological effect. Critics argue that introducing sievertide without standard definitions risks ambiguity.

See also: Sievert, Gray, Dose rate, Biological effectiveness, Radiation dose.