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

Give it two to three weeks before judging results, and don’t abandon your regular deodorant on day one. — Samantha Agate, Miami Herald, 5 Oct. 2026

Here, members of Forbes Business Council share one step businesses should take before launching an e-commerce platform to create a clear, seamless customer experience from day one. — Expert Panel®, Forbes.com, 2 Oct. 2026

The singer recently put out her eighth studio album, Popstar, to much critical acclaim and fanfare online, as her day one fans are taking a victory lap on social media. — Angel Diaz, Billboard, 30 Sep. 2026

The insoles have built-in arch support with memory foam footbeds, and they’re designed to hug your feet for a snug fit that feels broken in from day one. — Caley Sturgill, Southern Living, 29 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