Q: Which is correct: “I have no idea of the year, leave alone [let alone] the day”? I once came across an authoritative position on this, but I can’t remember the authority or, more importantly, what was authorized. I sure hope you can help.
A: The common idiomatic usage in both the US and the UK is “let alone,” not “leave alone,” so the sentence should read: “I have no idea of the year, let alone the day.”
Merriam-Webster’s Dictionary of English Usage says, however, that “leave alone” is occasionally seen in British English, where it “seems to be only a rather rare variant.”
Merriam-Webster’s says the phrase “let alone” is being used in this case “as a conjunction to introduce a contrasting example for purposes of emphasis.”
In sentences with “a negative construction or negative overtones,” the usage guide adds, the phrase means something like “much less.” In positive contexts, the meaning is close to “not to mention” or “as well as.”
(We briefly discussed “let alone” and similar constructions in a posting several years ago about the expression “not to mention.”)
The Oxford English Dictionary, which has examples of the usage dating from the early 19th century, says “let alone” is being used here colloquially in the sense of “not to mention.”
The earliest citation in the OED is from an 1812 short story by the Anglo-Irish writer Maria Edgeworth: “I didn’t hide, nor wouldn’t from any man living, let alone any woman.”
We’ll end this with an example from an 1816 letter by Jane Austen to her sister, Cassandra, that apparently refers to two of their six brothers:
“He does not include a maid in the list to be accommodated, but if they bring one, as I suppose they will, we shall have no bed in the house even then for Charles himself—let alone Henry. But what can we do?”
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