pi English · revision 15072

+ {{infobox|confidence=established|formation=borrowing|attested=15th century|origins=grc πῖ}}

+

+ ==Pronunciation==

+ * IPA: /paɪ/^(Roach et al. 2011)

+

+ ==Etymology==

+ It is the name of the Greek letter [[grc|πῖ|tr=pî]],^(MWU 2024)^(OED 1989) which is of Semitic origin.^(MWU 2024) Etymonline says it came from Phoenician, literally “little mouth”.^(Etymonline) As the mathematical constant, π stands for [[m|grc|περιφέρεια|tr=periphéreia|t=periphery]] (see [[periphery]]).^(Barnhart 1988)^(Etymonline)^(Hoad 1986)^(Collins 2023)

+

+ ==Earliest recorded meaning==

+ The name of the letter: the 15th century in Merriam-Webster.^(MWU 2024)

+

+ ==Semantic evolution==

+ The Swiss mathematician Leonhard Euler used π for the ratio of a circle's circumference to its diameter in Latin in 1748,^(Etymonline)^(Barnhart 1988)^(OED 1989) and the use is found in English from 1841.^(Barnhart 1988)^(Etymonline) In electrical engineering a pi network is from 1924, and in physics and chemistry pi electrons and bonds from 1929.^(OED 1989)

+

+ ==Timeline==

+ * 15th century – the letter pi.^(MWU 2024)

+ * 1748 – π for the circle ratio (Euler, in Latin).^(Etymonline)^(OED 1989)

+ * 1841 – pi (mathematics, English).^(Barnhart 1988)^(Etymonline)

+ * 1929 – pi electrons.^(OED 1989)

+

+ ==Modern meaning==

+ ===Noun===

+ # The 16th letter of the Greek alphabet (Π, π).^(AHD)^(Collins 2023)

+ # ''(mathematics)'' The ratio of the circumference of a circle to its diameter, a [[transcendental number]] of about 3.14159.^(AHD)^(Collins 2023)

+

+ ==Word family==

+ * [[pion]]

+ * [[pi meson]]

+

+ ==Related words==

+ * [[periphery]]

+ * [[pie]]

+

+ ==Usage notes==

+ Pi, jumbled printing type, is a variant of [[pie]].^(Etymonline)^(OED 1989)^(AHD) An old school slang pi, pious or sanctimonious, is from about 1870.^(OED 1989)

+

+ ==References==

+ {{reflist}}