March 14 is International Day of Mathematics – UNESCO declared it so at its 40^{th} General Conference in 2019 – and also Pi Day (that’s the constant Pi, not pie) in the US (where March 14 is written in month/day format – 3.14).

International Day of Mathematics observance is led by the International Mathematical Union, whose theme in 2021 is Mathematics for a Better World.

There’s also a Pi Approximation Day, observed on 22 July (22/7 in day/month format), since the fraction ** ^{22}⁄_{7}** is a common approximation of pi, accurate to two decimal places. And let’s not forget Two Pi Day, also known as Tau Day for the mathematical constant, observed on 28 June (6/28 in month/day format).

**Science istheway of my life.Itshows me things that Ihave only seen glimpses of before.**

*Rohan (age 9)*

**“But I’m fromahyperbolicspacewhere **

*π*can be four!”…My maths teacher still gave me zero

*Michael Hall*

Why are we reminding you of this?

On 14 March this year the Royal Institution of Australia (RiAus) decided to celebrate by launching the Cosmos Pi-ku 2021 competition. And now we’re just 25 days from the closing date for entries, of which we’ve already published a few.

To recap: in order to enter, you need to write a Pi-ku: that’s kind of like a haiku, only with more syllables. A haiku in English is generally accepted to be a poem of three lines and 17 syllables arranged in a 5–7–5 pattern.

A Pi-ku (for our purposes) is a poem of six lines and 23 syllables arranged in a 3–1–4–1–5–9 pattern (Pi to five decimal places: 3.14159).

To enter, write one of more Pi-kus and email them, including your name and a contact telephone number, here.

**My thoughts flytoirrationalskiesgeometricalabstractions gliding rapidly by**

*Robert Erlandson*

**SyracusewizArchimedesdreamedrocks with faces likerhombicosidodecahedrons**

*Jack Harris*

Entries close on Two Pi Day – 28 June, when we’ll announce the judging panel. Winners will be announced on Pi Approximation Day (22 July)

Entries will be judged for style, originality and alignment with science and Pi.

The top three entries will win a Cosmos digital subscription.

Would you like an example? Here’s *Adrienne*’s entry:

Maths is great

and

has a language

but

Italian for me

to keep my brain working and healthy

What are you waiting for: get writing.