How long is a day?

Did you say 24 hours? How about if someone says to come for a day – do you need more context before you know whether they mean until some afternoon or evening point or to stay the night? And how about if someone says you’ll get something by the end of the day?

Or did you say how long a day is depends on what time of the year and what latitude, because the sun is up for variable amounts of time? But does that mean that “three days” is longer in summer than in winter?

Of course we can be more precise when the context isn’t clear. But so often we want to be able to say “day” and just mean a contiguous span of 24 hours – either any span of 24 hours (say, starting right now and ending at the same clock time tomorrow) or one night plus one day, beginning at either sunset or sunrise (allowing, of course, the slight shift in sunrise and sunset times from day to day). In those cases, the problem may just be that day is not long enough.

Not the day. The word day. What you really want is a nice, luxuriantly long word, one that has, say, a letter for each hour – well, OK, a letter for each two hours, we’ll say, since there are hours of the day and hours of the night, and anyway 24 letters would be an awfully long word. How about a word that morphologically maps to the circadian cycle? And how about if, as an added bonus, it’s really hard to spell and confusing to pronounce?

Oh. Lost you on that last bit, did I? Well, so it goes. That’s what we have. The word, my friends, is nychthemeron, also spelled nycthemeron. It comes directly from Greek νυχθήμερον, which in turn formed it from νυκτ- (nukt-) ‘night’ and ἡμέρα (hemera) ‘day’. You may notice that the t in the one root and the h in the other have come together to make th, which is not pronounced like “t” and then “h” (or just like “t”) but is in fact θ, said like “th” as in “thin”; the collision of the two words in Greek made a sort of twilight zone where the “k” (κ) also became “kh” (χ), though we say it “k” now in English. Oh, and the stress is on the them, which can be said with the e as in “them” or, if you want to Anglicize further, can be said like “theme.”

And there it is. Night and day, you are the one… It’s a bit of a pity that this word is so unwieldly, because it could be quite useful in some contexts (such as hotels, where night means ‘nychthemeron’ but they always start at 3 or 4 pm and the last one – or the only one if you’re only there for one night – is a few hours short). And while “See you in twenty-four hours” is accurate but sounds cold and dorky, “See you in a nychthemeron” sounds poetic – though perhaps a bit frightening.

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