day one

noun

often capitalized D&O
: 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.
Third, embed controls from day one. Juan Arroyo, Forbes.com, 9 Sep. 2025 The company has a dedicated website where new hires can sign up for a welcome gift, watch setup videos, and join a forum to ask questions before day one. Roula Amire, Fortune, 9 Sep. 2025 And day one did not turn into the Freak-out of the Gen Alphas that elders might have predicted. Christopher Bonanos, Curbed, 5 Sep. 2025 As one of the cadre of uber-agents who famously departed William Morris and founded CAA in 1975, Ovitz says there was an informal understanding from day one at the new agency. Laurie Brookins, HollywoodReporter, 5 Sep. 2025 See All Example Sentences for day one

Word History

First Known Use

1971, in the meaning defined above

Time Traveler
The first known use of day one was in 1971

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Cite this Entry

“Day one.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/day%20one. Accessed 12 Sep. 2025.

Last Updated: - Updated example sentences
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