day one

noun

variants often Day One
Synonyms of day onenext
: 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.
Our fight from day one has never been to hold the tribe down. Ashley Sharp, CBS News, 15 Apr. 2026 This mindset was especially present on day one as the high for the day was 91°. Carolyn Burt, Hartford Courant, 15 Apr. 2026 That alone can be the difference between a five-day trip and a ten-day one. Lauren Schuster, Miami Herald, 14 Apr. 2026 Here's all the major news from CinemaCon 2026, day one. Wesley Stenzel, Entertainment Weekly, 14 Apr. 2026 See All Example Sentences for day one

Word History

First Known Use

1953, in the meaning defined above

Time Traveler
The first known use of day one was in 1953

Browse Nearby Words

Cite this Entry

“Day one.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/day%20one. Accessed 16 Apr. 2026.

Love words? Need even more definitions?

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

More from Merriam-Webster