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.
The Spaniard’s commitment to speaking English from day one was initially applauded, but that narrative changed when results deteriorated. Stuart James, The Athletic, 5 Feb. 2025 The block schedule would include an anchor day one day a week in which the students would attend all of their classes for a shorter length of time. Michelle Mullins, Chicago Tribune, 4 Feb. 2025 But compared to earlier games, there’s more here on day one than usual. Ars Technica, 3 Feb. 2025 And despite Trump's vow to issue an executive order on day one to delay the enforcement of a bipartisan law, TikTok still might be racing against the clock to strike a deal. Avery Lotz, Axios, 26 Jan. 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

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 16 Feb. 2025.

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!