There are 3 main definitions of PI in English:

Share this entry

PI 1

Syllabification: PI

Entry from US English dictionary

abbreviation

Private investigator.

Definition of PI in:

Share this entry

 

There are 3 main definitions of PI in English:

Share this entry

pi 2 Line breaks: pi

noun

1The sixteenth letter of the Greek alphabet (Π, π), transliterated as ‘p’.
Example sentences
  • This is true of no other letter of the alphabet except pi, and here the name is a natural development of the Semitic name pe.
  • Pi is the sixteenth letter of the Greek alphabet. In the system of Greek numerals it has a value of 80.
  • The western Greek alphabet changed pi into a backwards loop shape.
1.1The numerical value of the ratio of the circumference of a circle to its diameter (approximately 3.14159).
[From the initial letter of Greek periphereia 'circumference']
Example sentences
  • Saying that pi is 3.14 without addressing the fact that it goes on infinitely afterward overlooks the true essence of the number.
  • So far, pi has been calculated to 1.24 trillion decimal places with the aid of a supercomputer.
  • The circumference of a circle can be found by multiplying pi (which is equal to 3.14) by the diameter of the circle.
1.2 (Pi) [followed by Latin genitive] Astronomy The sixteenth star in a constellation: Pi Herculis
More example sentences
  • Lower letters are generally assigned to brighter stars, but a star designated pi is not necessarily the 16th brightest star of the constellation (for example, pi Puppis is number two in brightness in the constellation Puppis).
  • Pi Herculis is particularly noticeable for its reddish complexion and is an excellent place to begin studying the constellation.
  • The red giant Pi Leonis in the constellation of Leo the Lion has a radius 80 times larger than our own Sun.
1.3 [as modifier] Chemistry & Physics Relating to or denoting an electron or orbital with one unit of angular momentum about an internuclear axis: the π orbital system of the benzene molecule
More example sentences
  • Both of the electrons in the pi bond are found in the pi bonding orbital.
  • The lowest pi orbital of benzene is called the A2u orbital.
  • The bonding pi orbital is lower in energy than the atomic p orbitals, whereas the antibonding pi orbital is higher in energy than the atomic pi orbitals.

symbol

Back to top  
1 (π) The numerical value of pi.

Origin

Greek.

Words that rhyme with pi

ally, Altai, apply, assai, awry, ay, aye, Baha'i, belie, bi, Bligh, buy, by, bye, bye-bye, chi, Chiangmai, Ciskei, comply, cry, Cy, Dai, defy, deny, Di, die, do-or-die, dry, Dubai, dye, espy, eye, fie, fly, forbye, fry, Frye, goodbye (US goodby), guy, hereby, hi, hie, high, I, imply, I-spy, July, kai, lie, lye, Mackay, misapply, my, nearby, nigh, Nye, outfly, passer-by, phi, pie, ply, pry, psi, Qinghai, rai, rely, rocaille, rye, scry, serai, shanghai, shy, sigh, sky, Skye, sky-high, sly, spin-dry, spry, spy, sty, Sukhotai, supply, Tai, Thai, thereby, thigh, thy, tie, Transkei, try, tumble-dry, underlie, Versailles, Vi, vie, whereby, why, wry, Wye, xi, Xingtai, Yantai

Definition of PI in:

Share this entry

 

There are 3 main definitions of PI in English:

Share this entry

pi 3 Line breaks: pi

adjective

British informal
Short for pious.

Definition of PI in:

Share this entry

 

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.

Get more from Oxford Dictionaries

Subscribe to remove ads and access premium resources

Word of the day haughty
Pronunciation: ˈhôdē
adjective
arrogantly superior and disdainful