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 If that’s not enough, Black Ops 6 marks the first time a Call of Duty game will be available on Game Pass day one. Quentyn Kennemer, The Verge, 19 June 2024 Loading your audio article Since day one of his administration, the fossil fuel industry and its right-wing allies have disingenuously blamed President Joe Biden for increases in fuel prices, falsely claiming the administration was holding back fossil fuel production. Robert Weissman, The Mercury News, 15 June 2024 Consciousness has been a staple of his music since day one. Helena Andrews-Dyer, Washington Post, 15 June 2024 President Joe Biden during day one of the 50th G7 summit on Thursday in Fasano, Italy. David Ingram, NBC News, 14 June 2024 See all Example Sentences for day one 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'day one.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1971, in the meaning defined above

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

Dictionary Entries Near day one

Cite this Entry

“Day one.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/day%20one. Accessed 4 Jul. 2024.

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!