- (idiomatic, negative polarity item) Much less; to say nothing of; used after one negative clause to introduce another, usually broader and more important clause, whose negation is implied by the negation of the first.
- He couldn't boil water, let alone prepare a dinner for eight.
- (idiomatic, positive polarity item, rare) not to mention, as well as; used after one item, to introduce a further item which is entailed by the first.
- Sometimes used with the order of items reversed.
to say nothing of
- Charles J. Fillmore, Paul Kay, Catherine O'Connor (September 1988) "Regularity and idiomaticity in grammatical constructions: The case of let alone" Language (Vol.64 No.3) pp.501-538
- Mark Liberman (24 February 2011) "Much less/Or even" Language Log
- E. Ward Gilman (editor) Merriam–Webster's Dictionary of English Usage p.596, Merriam–Webster, 1994 ISBN 9780877791324.
- (transitive) To leave alone, let be; to stop bothering.
- I wish he would let me alone so I could get some sleep.
leave alone — see leave alone