Unless

//ənˈlɛs// conj

conj ·Uncommon ·Advanced level

Definitions

Conjunction
  1. 1
    Except on a specified condition; if not.

    "I’m leaving unless I get a pay rise."

  2. 2
    If not; used with counterfactual conditionals.

    "Who would know of Alexander or Caesar, or would respect the Stoics or the Peripatetics, unless they had been distinguished by the memorials of writers?"

  3. 3
    Except if; used with hypothetical conditionals.

    "Q. If Lieutenant P. had given the word "Fire," would you have fired, and at what?—A. I should not have known, unless he had told me what to fire at."

Synonyms

All synonyms
aside fromat least ifbarbarringbesidebesides

Example

More examples

"Don't stay in bed, unless you can make money in bed."

Etymology

From Middle English unlesse, earlier on lesse (modern on + less), from (not) on lesse (than) (“(not) on a less compelling condition (than)”). The quality of negation in the word and the lack of stress changed on to un-.

Related phrases

precisely unlessunless and untiluntil and unless

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.