fractionalsecond

Fractional second refers to any portion of a second expressed as a value less than one full second. In practice, fractions of a second appear in timekeeping, data timestamps, and scientific measurements. They can be written as decimal fractions of a second (for example, 0.25 s) or represented by subunits with SI prefixes such as milliseconds or nanoseconds.

Common subunits of the second include deciseconds (0.1 s), centiseconds (0.01 s), milliseconds (0.001 s), microseconds (0.000001 s), nanoseconds (0.000000001 s), picoseconds (0.000000000001 s), and femtoseconds (0.000000000000001 s). Decimal notation is standard in digital systems and scientific data. ISO 8601 timestamps can include a decimal fraction after the second, such as 2023-07-21T15:03:27.123Z.

Applications of fractional seconds span sports timing, physics experiments, astronomy, and computing. High-resolution timing enables precise event sequencing, logging, and synchronization across systems. Instruments such as quartz oscillators and atomic clocks provide sub-second accuracy, while electronic timing circuits, stopwatches, and time-stamping hardware record incremental fractions of a second.

Standards and concepts: the second is the base SI unit of time, with fractional subdivisions defined by decimal prefixes. In practice, fractional seconds must account for measurement uncertainty and potential rounding. In programming and data formats, fractional seconds are often managed with fixed or variable decimal precision or through explicit representations like nanoseconds since an epoch. The notion of a fractional second is thus a way to express time with finer granularity than one second.