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

From day one, Caliza built its own licenses and banking relationships rather than routing through other companies' infrastructure. — Aaron Stanley, Forbes.com, 21 July 2026

House District 100 deserves a representative who is ready to lead on day one. — Chris Vincent, Sun Sentinel, 20 July 2026

On the 72 nights of group stage matches, host cities saw declines in occupancy 44 times, compared to the same day one year earlier. — Miami Herald, 17 July 2026

Don’t expect your kid to get the hang of it on day one, and don’t force them to execute their routine perfectly every morning, without any fuss or pushback. — Parents, 17 July 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