day one

noun

variants often Day One

: the first day or very beginning of something

Synonyms of day one

• beginning
• start
• inception
• commencement
• alpha
• onset
• launch

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

Building something well on day one is only half the commitment. — Nick Chandi, Forbes.com, 16 Sep. 2026

Toronto began the day one game behind Cleveland in the race for the final AL wild card. — ABC News, 13 Sep. 2026

Speakers from left, Brett Gibson, Initialized Capital; Jen Wolf, Initialized Capital; Garry Tan, Initialized Capital, on Venture stage during day one of Web Summit 2022 at the Altice Arena in Lisbon, Portugal. — Kate Rooney,isabel O'Brien, CNBC, 11 Sep. 2026

Yom Kippur, the holiest day of the year for the Jewish people, is considered the day one's fate is sealed in the Book of Life. — Bailey Allen, The Providence Journal, 10 Sep. 2026

Word History

First Known Use

1953, in the meaning defined above

Rhymes for day one

• begun
• grandson
• gudrun
• handgun
• homespun
• outdone
• outrun
• pashtun
• redone
• rerun
• shotgun
• someone