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

Today’s live coverage of day one of the trial of Duane Keith Davis, who was indicted in 2023 in Tupac Shakur’s death, has ended. — Aditi Sangal, CNN Money, 17 Aug. 2026

Incident response should be built into the deployment strategy from day one. — Hugo Sarrazin, Forbes.com, 17 Aug. 2026

The setup takes an API key configured as a request header, which is the same pattern used across professional developer tools, giving technical teams full control from day one. — Roy Stephen Canivel, Footwear News, 12 Aug. 2026

Pros Earns a competitive APY with no minimum balance required to earn the full rate, so your money works hard from day one. — Kelsey Neubauer, CNBC, 12 Aug. 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