unless

American  

[uhn-les, uhn-] / ʌnˈlɛs, ən- /

conjunction

1. except under the circumstances that.

   I'll be there at nine, unless the train is late.

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preposition

1. except; but; save.

   Nothing will come of it, unless disaster.

unless British  

/ ʌnˈlɛs /

conjunction

1. (subordinating) except under the circumstances that; except on the condition that

   they'll sell it unless he hears otherwise

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preposition

1. rare except

Etymology

Origin of unless

1400–50; late ME prepositional phrase on less (also o less(e) , earlier upon less ) on a lesser footing or condition (than); first used as a preposition and conjunction in the early 16th century; see on, less

Example Sentences

Unless extra supplies can be found, a lack of fuel could lead to further disruption and cancellations heading into the peak summer holiday period.

From BBC • May 3, 2026

Unless something big changes, Americans should expect gasoline prices to keep rising.

From Barron's • Apr. 30, 2026

Unless the Strait of Hormuz fully reopens, shortages in the physical supply of oil could result in a sharp spike in energy costs, they said.

From MarketWatch • Apr. 21, 2026

Unless LeBron James can pull off the second-greatest feat of his 23-year career.

From Los Angeles Times • Apr. 17, 2026

Unless it wasn’t him she was looking at.

From "Half Upon a Time" by James Riley