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

These are all things that are going to need to be thoroughly investigated as part of our pledge to hold the crooks accountable, beginning on day one. — Lauren Peller, ABC News, 4 Nov. 2026

Regardless of how thoughtlessly Rainbeau might be acting, Rosa has had it out for her since day one. — Rafaela Bassili, Vulture, 3 Nov. 2026

Explainability belongs in the same place, written into the design document from day one, next to the accuracy targets rather than bolted on before an audit. — Aritra Pal, Forbes.com, 30 Oct. 2026

As day one of the sale winds down, Ingordo decides to switch things up. — Dana O’Neil, CNN Money, 30 Oct. 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