day one

noun

variants often Day One
Synonyms of day onenext
: the first day or very beginning of something

Examples of day one in a Sentence

We've known this about the project since Day One. since day one of this project, we've always insisted that we would create the best product possible without any consideration of cost
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
At our newest campus in Haverhill, Massachusetts, for example students will train in a 25,000-square-foot facility equipped with interactive shifting simulation and a new curriculum that focuses on hands-on learning from day one. Samantha Greenberg, Hartford Courant, 7 Apr. 2026 That moon loo has been part of the Artemis 2 conversation since day one of the mission, when its urine function went offline and was fixed by mission specialist Christina Koch, with guidance from Mission Control. Tariq Malik, Space.com, 5 Apr. 2026 That requires a people strategy powered by technology—with tech and talent leaders at the table, building in lockstep from day one. Teuila Hanson, Fortune, 3 Apr. 2026 By March 10, General Dan Caine, chairman of the Joint Chiefs of Staff, was saying Iranian ballistic missile attacks had fallen 90 percent from day one and one-way drone attacks 83 percent, while more than 50 Iranian naval vessels had been hit in the opening stage of the war. Micah McCartney, MSNBC Newsweek, 1 Apr. 2026 See All Example Sentences for day one

Word History

First Known Use

1953, in the meaning defined above

Time Traveler
The first known use of day one was in 1953

Browse Nearby Words

Cite this Entry

“Day one.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/day%20one. Accessed 11 Apr. 2026.

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