We all now know that NOx chemicals are a really, like, terrible thing you find in diesel fuel, and we all know this even though most of us have only the vaguest idea what NOx chemicals are.
First, what they're not. They're not N2O, which is laughing gas: but this is only to be expected, really, because the x in NOx comes at the end of the word and not in the middle.
No, NOx is either NO (nitric oxide) or NO2 (nitrogen dioxide).
You actually produce NOx chemicals when you burn most sorts of stuff, and in a city where there are a lot of vehicle engines burning fuel then the NOx chemicals can be seriously, well, noxious. They damage people's lungs and hearts, they tend to encourage genetic mutations, and they form smog and acid rain.
The good news is that NOx gases break up methane, so they are at least a force for global cooling.
NOx chemicals can also be formed by lightning, which is rather neat as a Nox is a unit of illuminance...through on the other hand, Nox is also the Roman way of spelling Nyx, who is the Greek goddess of the night.
Nox is a tiny place in Shropshire, England:
And, nearly as big as the hamlet of Nox, is Atrophaneura nox, the Malayan batwing butterfly:
As far as I know, the hamlet and the butterfly are both entirely harmless.
Word To Use Today: nox or NOx. The butterfly is presumably named after the goddess, and the hamlet is named after a family called Nock, who owned the local pub. The gas word is interesting, being made up of the chemical symbols for Nitrogen and Oxygen, plus the letter x, which is used in its mathematical sense of whatever.
The similarity of NOx (as in chemicals) to the word noxious is an accident. Noxious comes from the Latin noxa, which means injury.