One letter

, my own translation of the Dutch original


A terrabyte. That’s really a lot of data. One thousand gigabytes, a million megabytes. The pure text for 67 kilometres (41 miles) of bookshelf full of paperbacks with 30 line 50 character pages. Over half a million photo JPGs from an average digital camera. Yet an external disk with such a huge capacity is in the shops for tens of dollars or pounds, or else you get two of half that size.

That’s what many people think. But it ain’t so. There are no terrabytes in this world. There ARE terabytes. And for those the above numbers hold.


In the sequence yocto (10−24), zepto, atto, femto, pico, nano (10−9), micro, milli (10−3), [nothing], kilo (103), mega and giga, the next one is indeed tera, with a single r. Then follow peta (1015), exa, zetta and yotta (1024).

Tera is not terra and it is not from the Latin word terra that means ‘earth, soil, region’.

What tera was derived from I read in Wikipedia: the Greek word τέρας meaning ‘monster’. Analogous, no doubt, to the prefix giga, which is from a word for ‘giant’: γίγας.


Many people mix up the single r of tera and the double rr of terra. Here for example a classics scholar does that, although he could have known better. I sent him an e-mail with the goading subject “Pun or negligent ignorance?”. I know he does read my messages, because later on he replied to another one. Not this time though, and he made no correction. Up to him.


Three days ago I noticed a tweet about a fire in the Dutch town of Zevenaar. I used to live in that small city, so I was curious where exactly the fire was. A company called Promens in the Einsteinstraat. Yes, right.

While wandering about the Google Map I noticed conspicuous street names in a planned or perhaps already built extension of good old industrial estate Hengelder. Intriguing names: Zepto, Exa, Hecto, and also Terra. Right, that must be a mistake by the map makers, I thought, so immediately I sent a correction to Google Maps, because now we can.

Well, but the same error is also on Bing Maps. So is it really a mistake the map makers made, or is this simply the name they got through from the municipal authorities?


It’s the latter. In the minutes of a 20 May 2008 town council meeting, I found the decision to so name those streets, including the wrong “Terra” instead of ‘Tera’. I quote and translate:

The following street names are proposed:
Zepto, Nano, Micro, Hecto, Terra, Exa, Mega and Giga.

(Also a pity and a bit strange: the URL of that council meeting, when clicked from the hyperlink in another page, produces a “403 Forbidden” error message. But after an extra ‘enter’ the page address does work. Why not in one go?)


So be it and so it is.

10 September 2013

I received an e-mail from the municipal authorities in Zevenaar. They were already aware of the mistake. It will be corrected where it wasn’t already.

All is well that ends well.

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