pi
peye
Pi (noun) means a letter of the Greek alphabet. Example: “The professor wrote out several Greek letters, including pi, on the board.”
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.
"The teacher explained that pi never ends and never repeats."
"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
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Word forms
- Plural
- pis
- Third person singular
- pies
- Past tense
- pied
Fill the gap
Can you complete this real example?
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."
Synonyms
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Frequently asked questions
What does “pi” mean?
The word “pi” means a letter of the Greek alphabet. In plain terms, either the Greek letter, or the famous circle-ratio number roughly equal to 3.14.
How do you pronounce “pi”?
“Pi” is pronounced peye (/paɪ/ in IPA).
How do you use “pi” in a sentence?
Here is “pi” used in a sentence: “The professor wrote out several Greek letters, including pi, on the board.”
What part of speech is “pi”?
“Pi” is a noun.
Where does the word “pi” come from?
The word “pi” comes from Greek. From the Greek letter name pi; its mathematical use began because it's the first letter of the Greek word for "periphery/circumference.".
Is “pi” a common word?
“Pi” is a fairly common word in modern English, usually learned at around the B2 level.
How many meanings does “pi” have?
“Pi” has 2 distinct senses listed in this dictionary. The most common is: a letter of the Greek alphabet.
Is pi a rational or irrational number?
Pi is an irrational number, meaning it cannot be written exactly as a simple fraction, and its decimal expansion continues forever without repeating. Its value begins 3.14159 and goes on endlessly.
What is the difference between pi and 22/7?
The fraction 22/7 is a common approximation of pi, but it is not exactly equal to it. Pi is an irrational constant of about 3.14159, whereas 22/7 works out to roughly 3.142857.
What is the difference between the Greek letter pi and the number pi?
Pi is a letter of the Greek alphabet, written as the symbol for the character, and that same symbol is used in mathematics to represent the constant of about 3.14159. So the letter is the character itself, while the number is the value it stands for.
How is pi used with a circle's diameter?
Pi represents the ratio of a circle's circumference to its diameter, so multiplying the diameter by pi gives the circumference. This fixed relationship holds true for every circle regardless of its size.
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