This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.Find sources: "ISO 31-2" – news · newspapers · books · scholar · JSTOR (December 2007) (Learn how and when to remove this template message)
The topic of this article may not meet Wikipedia's general notability guideline. Please help to demonstrate the notability of the topic by citing reliable secondary sources that are independent of the topic and provide significant coverage of it beyond a mere trivial mention. If notability cannot be shown, the article is likely to be merged, redirected, or deleted.Find sources: "ISO 31-2" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message)

ISO 31-2 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to periodic and related phenomena.

Its definitions include:

Quantity Unit Remarks
Name Symbol Name Symbol Definition
period, periodic time T second s
time constant of an exponentially varying quantity τ second s