Q: In my readings of older material, I often see the word “sennight” (a k a, a week). Is it still used in British English, like “fortnight” (two weeks), or is “sennight” now archaic?
A: The word “sennight,” an old construction meaning “seven nights,” is now archaic, according to the Oxford English Dictionary. So you wouldn’t use it today unless you were writing historical fiction or drama.
In the OED’s definition, it means “a period of seven (days and) nights; a week.” So a “sennight” is the same thing as a week.
The term is derived from the Old English words seofon (seven) and nihta (nights), and it was originally written as two words. Some early forms recorded in the OED are “VII nihta” (800s), “sefenn nahht” (circa 1200), and “seuen nyght” (c 1386).
The first one-word version in the OED, “seoueniht,” may date from the late 1100s. It’s from Layamon’s Brut, a Middle English poem written sometime before 1200: “Seoueniht he wes þære.” (“Seven nights he was there.”)
Other one-word (or sometimes hyphenated) versions followed, and they continued to show up in English writing into the 19th century. Here, for example, are some widely separated sightings:
“A sefenneghte after that Murdok of Fyche was take away” (from 43rd Reports of the Deputy Keeper of Public Records, dated 1414).
“The crosse windes … held him in the Downes almost a seavennight before they would blow him over” (from Sir John Finett’s Finetti Philoxenis, recollections written sometime before 1641).
“My love for Nature is as old as I; / But thirty moons, one honeymoon to that, / And three rich sennights more, my love for her” (from Alfred Lord Tennyson’s poem Edwin Morris, 1851).
The word was also used to mean “a week from” or “a week ago” in constructions like these: “this day sennight” (a week from today); “Tuesday sennight” (a week from Tuesday); “Friday come a sennight” (a week from Friday); “Monday was a sennight” (a week ago Monday).
The OED’s first known example of this usage is also from Layamon’s Brut. Here’s the Middle English: “Ȝif ȝe spekeð mid rihte comeð to-dæi a seouen-nihte.” (“If you speak with right, come today sennight.”)
As you might expect, just as a “sennight” meant seven nights (one week), “fortnight” means fourteen nights (two weeks).
The OED explains that “fortnight,” which dates from the late 900s, is a “contracted form of Old English feowertyne niht” (fourteen nights).
“Fortnight,” unlike “sennight,” has survived into our own time and is a household word in Britain, where it’s found every day in news reports. In the US, however, “fortnight” is much less common and conveys an air of quaintness.
You may be wondering why these words used “nights” instead of “days” as a measurement of the passage of time. This is a remnant of a tradition that was observed in many ancient civilizations.
Max Müller, a 19th-century philologist and a renowned Sanskrit scholar, wrote that “time was measured by nights, and moons, and winters, long before it was reckoned by days, and suns, and years” (Lectures on the Science of Language, 1861).