Pi is a number. You write it with the Greek letter π.

PiPi（圓周率） is a number是一個數。You write it你會寫成 with the Greek letter π希臘字母π。

For any circle, if you take the distance all the way round (the circumference) and divide by the distance across through the centre (the diameter), you get the same number: pi.

For any circle對任何一個圓來說, if you take the distance all the way round (the circumference)如果你拿繞一圈的距離（circumference，圓周長） and divide by the distance across through the centre (the diameter)除以穿過圓心的那段距離（diameter，直徑）, you get the same number: pi你會得到同一個數：pi。

It is a little more than 3.14, and the digits after the point go on for ever without a repeating pattern. School maths uses 3.14 or 22/7 as a stand-in; the real number never ends.

It is a little more than 3.14它比3.14多一點點, and the digits after the point go on for ever without a repeating pattern小數點後面的數字會一直延續下去，不會重複。School maths uses 3.14 or 22/7 as a stand-in學校數學用3.14或22/7當作代替; the real number never ends但真正的那個數是沒有盡頭的。

The name comes from the Greek letter, and that letter was taken because it begins the Greek word for the rim, the periphery, of a circle. A Welsh teacher, William Jones, is first known to have used π this way in a book in 1706.

The name comes from the Greek letter這個名字來自那個希臘字母, and that letter was taken because it begins the Greek word for the rim, the periphery, of a circle而選那個字母，是因為它是希臘文裡「圓的邊緣、周邊」這個字的字首。A Welsh teacher, William Jones一位威爾斯老師William Jones, is first known to have used π this way in a book in 1706是目前已知最早在1706年的一本書裡這樣使用π的人。

In English the word is spoken like pie. It is ordinary in maths class and in any talk about circles.

In English the word is spoken like pie在英文裡這個字唸起來像pie。It is ordinary in maths class and in any talk about circles在數學課和任何講到圓的場合裡，這是個很普通的字。