Q: To quote James Taylor, would you please “shed a little light” on this? Is the fixture a “night light,” “night-light,” or “nightlight”?
A: It depends on which standard dictionary you consult.
The word is hyphenated, “night-light,” in four US dictionaries: American Heritage, Merriam-Webster, Merriam-Webster Unabridged, and Dictionary.com (based on the old Random House Unabridged).
However, it’s two separate words, “night light,” in Webster’s New World and in a British dictionary, Collins. And it’s a single unhyphenated word, “nightlight,” in these four British dictionaries: Lexico (the former Oxford Dictionaries Online), Macmillan, Cambridge, and Longman.
Our vote goes to the British foursome, and “nightlight.” As we’ve written several times on the blog, most recently in 2019, many compounds start out as two words, then acquire a hyphen, and finally become a single word.
We predict that as time goes on, the form “nightlight” will become more widely adopted in standard dictionaries.
When the term entered English, hyphenated at first, it didn’t mean something plugged into an electrical outlet, or even using candlelight. It meant “the faint natural light perceptible at night,” according to the Oxford English Dictionary, an etymological dictionary based on historical evidence.
The OED, which gives the term as “night light,” cites this 17th-century example as the earliest known use in writing: “Nachtlicht, night-light, Night-shine” (from a 1648 Dutch-English dictionary by Henry Hexham).
Elizabeth Barrett (before she married Robert Browning) used this sense of “nightlight” poetically in her verse play A Drama of Exile (1844), rhyming the line “In the sunlight and the moonlight” with “In the nightlight, and the noonlight.”
But by that time, “nightlight” had also become a household item. The OED defines this sense as “a light source designed to provide faint illumination in a room at night; spec. a small, thick, slow-burning candle or an electric light of low power, used in the bedroom of a child or sick person.”
The dictionary’s earliest example is from a long poem by Robert Bloomfield, Good Tidings, first published in London in 1804. Here he describes a mother at her son’s sickbed: “Hour after hour, when all was still beside, / When the pale night-light in its socket died, / Alone she sat.”
Such a useful word was bound to survive into the age of electricity. This OED citation is from the late 20th century: “The light’s meager appetite for electricity … makes it the most environmentally sensible night-light around.” (From a British magazine, Harrowsmith Country Life, Dec. 14, 1994.)