# Pi Day

> English word · Proper noun · IPA /ˈpaɪ deɪ/

## Definitions
1. March 14th, an annual celebration of the mathematical constant π (pi).

## Etymology
pi + day, from the date March 14th in the month/day format (that is, 3/14), 3, 1 and 4 being the first three significant digits of the mathematical constant π.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/pi-day