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**Clarification:** The 1829 article "Farming Country Parishes" mentions π as a Greek letter, not a number. Thanks to J. Migchielsen for pointing this out this discrepancy in the comments below, and to Femke for raising the question of whether the data in our "Pi Chart" apply to the number Pi only or also the letter. (See the author's response in the comments.) — Alison Bert, Editor-in-Chief[divider]

The number π is a mathematical constant – the ratio of a circle's circumference to its diameter, approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, though it is also sometimes spelled out as "pi."

The first paper published and indexed in Scopus mentioning pi 'π' dates back to 1829 and was called "Farming Country Parishes," published by *The Lancet*. The earliest published work that has actually had a measurable influence in research is the work "Ueber die Zahl π" (About the number π), published in German in *Mathematical Annals* in 1882. It received 23 citations.

The most significant paper in the literature that received notable citations does not appear until more than 30 years later, authored by I Langmuir in 1916: "The constitution and fundamental properties of solids and liquid, Part I. Solids," in the *Journal of the American Chemical Society*. This paper attracted 1,995 citations!

It seems there is a long history of "pi," and I would have thought its application would have mainly been found in physics and mathematics; however, that's not the case, as you can see from the chart below.[divider]

# Pi chart

This graphic from SciVal shows that *π* has had an influence across a vast array of disciplines.

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# Elsevier Connect Contributor

Iris Kisjes (@Kisjes) has worked at Elsevier for seven years, the past four in communications. She is currently Senior Corporate Relations Manager, based in Amsterdam. She has a keen interest in the knowledge economy, especially in relation to the valorization of science and the longevity of the higher education system.

March 14, 2014 at 9:08 pmLa importancia de Pi es más destacada en biología y en medicina. Larga vida.

ReplySankar

March 17, 2014 at 7:04 amI feel proud to be a Mathematics graduate!!!

ReplyFemke

March 18, 2014 at 9:19 amDo the SciVal data you are showing apply to the number Pi only, or also the letter Pi?

ReplyMarch 19, 2014 at 1:57 pmHi Femke, the search I did actually covers both the letters "Pi" and the symbol though you need to be aware that the slice of data are taken from 2009-2013 so the total number will be much smaller than the Scopus figures.

March 18, 2014 at 7:05 pm"Farming Country Parishes" does not mention the number π. It mentions the letter π, in a short Greek text. The article by I. langmuir _does_ mention the number π; once, in a formula.

ReplyMarch 19, 2014 at 2:01 pmYou are right the search performed looks at where the symbol π is used or there "Pi" is present in the title, abstract or keyword. Hence, it will not discriminate between π as a symbol or letter.