Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

From PACS to PhySH


Physics keeps changing and so do classification and subject indexing. Arthur Smith recalls the final updates to the Physics and Astronomy Classification Scheme (PACS) and the development of the Physics Subject Headings (PhySH), and ponders future directions.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Fig. 1


  1. Krumhansl, J. A. & Trigg, G. L. Indexing and classification. Phys. Rev. Lett. 34, 1065 (1975).

    Article  ADS  Google Scholar 

  2. Physics Classification Workshop. Physics classification — Boston, MA — November 28, 2011. Physics Classification Workshop (2011).

  3. World Wide Web Consortium. Simple knowledge organization system. (2012).

  4. Conover, E. New physics classification scheme unveiled. APS News (2016).

  5. American Physical Society. PhySH now publicly available. APS Physics (2018).

  6. US National Library of Medicine. Medical subject headings. (2018).

  7. American Astronomical Society. (2013). Unified astronomy thesaurus. Astrothesaurus (2013).

  8. The SAO/NASA Astrophysics data system. (2018).

  9. EMBL-EBI. Data collections. (2018).

  10. Marcus, G. Deep learning: a critical appraisal. Preprint at arXiv (2018).

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Arthur Smith.

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Smith, A. From PACS to PhySH. Nat Rev Phys 1, 8–11 (2019).

Download citation

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing