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.
President-elect Donald Trump has made day one promises that will upend gun violence prevention efforts nationwide. Raja Krishnamoorthi, Newsweek, 16 Dec. 2024 Trump has vowed to impose higher tariffs on Mexico, Canada and China on day one of his presidency. Elisabeth Buchwald, CNN, 16 Dec. 2024 What does that mean for you on day one of the Trump administration? CBS News, 15 Dec. 2024 On day one, Summer won the gold in the 400-meter freestyle, with a world record time of 3:50.25 seconds, lowering the previous record of 3:51.30 set by Li Bingjie of China in 2022. Paras J. Haji, Forbes, 13 Dec. 2024 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 21 Dec. 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!