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.
Most recently, Marlyne Barrett, who played charge nurse Maggie Lockwood since day one, confirmed her exit. EW.com, 2 Sep. 2025 Build your ethical guardrails from day one. David Henkin, Forbes.com, 2 Sep. 2025 In other words, even if his performances have not been the best, few expected to see the Alexander-Arnold of his Liverpool best from day one under such conditions. Mario Cortegana, New York Times, 1 Sep. 2025 This effort is being led by the same figures who fought the commission from day one and lost. Suzette Valladares, Oc Register, 31 Aug. 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 8 Sep. 2025.

Last Updated: - Updated example sentences
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