SIseconden

SIseconden is a term found in niche discussions about time measurement within the framework of the International System of Units (SI). It is not an officially defined unit by the International Bureau of Weights and Measures (BIPM) and does not appear in the SI Brochure.

In some speculative or fictional contexts, SIseconden is described as either a naming variation for the SI second or as a proposed subunit of time intended to facilitate ultra-precise measurements. Because there is no formal definition, the exact size of an SIseconde is not standardized, and proposals have varied. Some writers treat it as simply the second in certain linguistic contexts, while others imagine it as a distinct decimal subdivision comparable to microseconds or nanoseconds, chosen for hypothetical or pedagogical reasons.

Relation to the official unit: The official SI unit of time is the second, defined by 9,192,631,770 periods of radiation corresponding to the Cs-133 atom transition. Any term such as SIseconden would only have a concrete meaning if an official body assigned it a specific value, which has not occurred. As a result, SIseconden remains primarily of interest in linguistic, theoretical, or fictional discussions rather than practical metrology.

See also: International System of Units, metrology, second, BIPM.