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Symbol | Definition |
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≡ | exactly equal |
≈ | approximately equal to |
= | equal to |
digits | indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …) |
Femtosecond is equal to 10-15second (unit of time), comes from a combination of the metric prefix femto (f) with the second (s). Plural name is femseconds with symbol is fs.
A day is a unit of time. In common usage, it is either an interval equal to 24 hours or daytime, the consecutive period of time during which the Sun is above the horizon.