Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- conj. Except on the condition that; except under the circumstances that: "Exceptional talent does not always win its reward unless favored by exceptional circumstances” ( Mary Elizabeth Braddon).
- prep. Except for; except.
Century Dictionary and Cyclopedia
- If it be not that; if it be not the case that; were it not the fact that; if … not; supposing that … not.
- For fear that; in case; lest.
- [By omission of a verb, implied in the context, unless may have the force of ‘except,’ ‘but for’: as
- Synonyms Except, Unless. Except could once be used as a synonym for unless, but the words have now drawn entirely apart. Unless is only a conjunction; except is only a preposition. Except introduces an exception to a statement which is otherwise general: it may be followed by a clause when connection is made by a particle, as when, that, as, while, or especially another preposition: the omission of such connective makes the structure archaic. Unless introduces a clause, or the abbreviation of a clause, indicating a limitation or condition.
Wiktionary
GNU Webster's 1913
- conj. Upon any less condition than (the fact or thing stated in the sentence or clause which follows); if not; supposing that not; if it be not; were it not that; except.
Etymologies
- onlesse, from on lesse, from on a less condition (on became un-) (Wiktionary)
- Middle English unlesse, alteration (influenced by un-, not) of onlesse : on, on; see on + lesse, less; see less. (American Heritage® Dictionary of the English Language, Fourth Edition)
Examples
“You continue thus to deal out the entire pack in successive rows, each row completely blocking the preceding one unless the removal of a card releases the one above it, or _unless the removal of cards in the upper rows_ (Rule II) releases that card from above.”
“The most important formality in English law, in making contracts for the sale of goods, with which a broker must comply, in order to make the contract legally enforceable by his principal against the third party, is contained in section 4 of the Sale of Goods Act 1893, which (in substance re-enacting section 17 of the Statute of Frauds) provides as follows: -- "A contract for the sale of any goods of the value of ten pounds or upwards shall not be enforceable by action unless the buyer shall accept part of the goods as sold, and actually receive the same, or give something in earnest to bind the contract, or in part payment, or _unless some note or memorandum in writing of the contract be made and signed by the party to be charged or his agent in that behalf_.”
Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria"
“unless shaking your boobage, pouting your lips, and giving faintly dead eye stares is acting, Scarlett Johannsson needs to find another line of work..unless its with Woody Allen because the man can take a talentless hack and make her an Oscar winner Mira Sorvino anyone?”
“a couple of minutes over his financial affairs, unless, _unless_, as you foresaw might happen, he had need of a large lump sum.”
“The conjunctions _if, though, unless, except, whether_, and _lest_, are generally signs of the _Subjunctive_; as, "_If_ I _love; unless_ I”
“I say this because it's not often we hear anyone use the term unless they are asking someone else to say it to them.”
The Huffington Post: Agi Smith: Why Don't People Say 'I'm Sorry'?
“Avoid the term unless it is in a direct quote, and then define it.”
Simon & Schuster: Essential Guide to Business Style and Usage
“I can't explain why this happened, but it's a huge opportunity for anyone in the 'silver' bracket who's fed up and wants to create a blog or newspaper column so everyone else will know about it but don't use "Fed Up" as your title unless you want a complete set of Rick Perry's teeth marks in your rear end.”
“In the future, I will avoid appearing on anything with "morning" in the title unless of course, it's "Good Morning America.”
“The Times editor, James Harding, has defended the paper's plan to place its online content behind a paywall, claiming the internet could "wipe out" the title unless charges are introduced.”
Lists
These user-created lists contain the word ‘unless’.
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-more or -less
Words ending with *more or *less, more or less. Many of theses terms also appear on the list The -less Said, which see.
schemaless, jobless, endless, useless, unless, guileless, wireless, regardless, homeless, nevertheless, countless, doubtless and 434 more...
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National Library Agenda Summit
nla2006, summit, agenda, library, ala, diversity, education, learning, continuous, scan, environmental, plan and 646 more...
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Basic English Vocabulary
Very basic words for ESL students.
a, abandon, ability, able, abortion, about, above, abroad, absence, absolute, absolutely, absorb and 4334 more...
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my dictionary
able, abnormally, abroad, absent, abstract, acceptable, acceptance, access, accessible, accession, according to, account and 4551 more...
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The things they carried (List 2)
Listening to this as an audio book for the second time. Tim O'Brien uses simple words and phrases to great effect. Very few unfamilar and big words . The writing style reminds me of words from Joh...
The, Things, They, Carried, meant, fond, By necessity,, presented to him, far beyond, against the brick..., reaching, taut and 2940 more...
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Ruby Reserved Words
alias, and, begin, break, case, class, def, defined?, do, else, elsif, end and 26 more...
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OM3 Lesson 17
newscaster, storm, severe, by, may, in fact, snow, viewing area, bridge, overpass, icy, become and 19 more...
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SERENDIPITY Accidental Discoveries in...
catalyst, vinyl, sythesis, straightforward, sincere, purify, pseudo, inhibitor, exasperate, endeavor, conception, conceive and 19 more...
Tweets
Looking for tweets for unless.

MikeyC Edit of yesterday's post:
When used with a negative verb, it means "if it is not the case that it is not the case", which, as Prof GK Pullum has pointed out to me, is a brainful. e.g. sentence "Unless Mary doesn't study, she will pass". Ouch! Jul 1, 2009
MikeyC When used with a negative verb, it means "if it is not the case that it is not the case", which, as Prof GK Pullum has pointed out, is a brainful. e.g. sentence "Unless Mary doesn’t study, she will pass". Ouch! Jun 30, 2009
gangerh Derives, I read, from the words 'upon less' and has nothing to do with the prefix 'un'. Mar 8, 2008