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.
Of the two brothers, Jeremiah is the antagonist of the season, mainly because fans have been rooting for Conrad and Belly since day one, while Jeremiah stands in their way. Olivia Petter, Vogue, 16 Sep. 2025 Schenker has kept this laser focus from day one. Cynthia Littleton, Variety, 16 Sep. 2025 Build employee experience into the design from day one. Erika Andersson, Forbes.com, 16 Sep. 2025 But don’t expect to charm your local cafe on day one. Lane Nieset, Travel + Leisure, 14 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 18 Sep. 2025.

Last Updated: - Updated example sentences
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