**Post 9/29 in the Staffrm #29daysofwriting challenge: The numbers 1 to 5**

Taking my inspiration from the intrepid unicyclist, I've picked number prefixes for today's etymology post. If you're looking for meaningful ways to get numeracy into your classroom, this is slightly better than "count the number of exercise books as we hand them out".

Let's start with

*uni*. As with many of the number prefixes, this comes from the Latin

*unus*, meaning one. There are lots of

*uni*words where the prefix means one - uniform, using

*forma*(shape, manner or type), unison, using

*sonus*(sound), unicorn, using

*cornu*(horn). There are then the words linked directly to the root, like unit and union.

Next we go to

*bi*. which comes from

*bis*(twice) - the word for the number two,

*duo*, gives us other related words, and provides the root for many of the Romance languages (e.g.

*deux*in French). We get bicycle, binoculars, biennial, and the more mathematical binary and bisect, using

*secare*(to cut or intersect).

Now

*tri*, from

*tres/tria*- we get triangle via the very specific

*triangulus*(three-cornered). Confusingly, we also get the same prefix from Greek - and this gives us words like tripod and triad.

*Quad*is one of my favourites, coming from

*quattour*(four), but with links to

*quadratus*(square). It seems misplaced to name a quadratic as such when its highest power is two, but returning to the Latin root, we can see exactly where this name has come from, perhaps also preserving one of the most fundamental features of quadratic expressions - that they relate to area, two dimensions and (originally) to squares.

*Quin*unfortunately doesn't get much of an outing, as it gets replaced mathematically by the Greek

*pent*(five), giving us pentagon and pentacle. Rather fantastically though, the word "quintessence" traveled all the way from Latin

*quinta essentia*- literally the "fifth essence" or the fifth element (after earth, air, fire and water), used to describe the substance that heavenly or cosmic bodies were made of - to the current physical usage of quintessence, proposed as a fifth fundamental force. It even has an equation.

You'll probably get some more number prefixes tomorrow - I've only managed the fingers on one hand. We've not even got to dec- or cent- yet, and I'm quite enjoying using the Latin dictionary I haven't touched for ten years.

In the meantime, Happy Pancake Day, and I thoroughly recommend geeking out and watching two chaps from UCL tell you how to make the perfect pancake.

*Image credit: http://wellcomeimages.org/indexplus/image/L0013864.html, CC BY 4.0,commons.wikimedia.org/w/index....*

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