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.
These people promised to lower costs on day one. ABC News, 19 Oct. 2025 He's been a staunch supporter of the death penalty from day one, as illustrated by the toy electric chairs on his desk. Haley Bemiller, Cincinnati Enquirer, 19 Oct. 2025 She’s been chunky since day one. Daniella Gray, MSNBC Newsweek, 17 Oct. 2025 This collection is a love letter to New York City style, something that’s been a part of me since day one. Christopher Claxton, Billboard, 16 Oct. 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

Browse Nearby Words

Cite this Entry

“Day one.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/day%20one. Accessed 23 Oct. 2025.

Last Updated: - Updated example sentences
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