noun
pi
peye
noun
1
A letter of the Greek alphabet.
"The professor wrote out several Greek letters, including pi, on the board."
2
The mathematical constant (about 3.14159) representing the ratio of a circle's circumference to its diameter.
"You need pi to calculate the area of a circle."
"Students memorize pi to several decimal places for fun."
How to Use Pi
Learner’s notesIn plain EnglishEither the Greek letter, or the famous circle-ratio number roughly equal to 3.14.
Easily confused with
Common pairings
calculate pi
digits of pi
pi day
Word Forms
pied past tense, pis plural, pis plural, pies singular
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The professor wrote out several Greek letters, including _____, on the board.
Etymology
From the Greek letter name pi; its mathematical use began because it's the first letter of the Greek word for "periphery/circumference."