day one

day one noun: the very beginning.

Noun

day one (plural day ones)

The very beginning.
- I've been with the project since day one.
(US, slang) A close, longtime friend, one who has been around since the beginning.
- Raise a cup up for all my day ones; two middle fingers for the haters […]2017 March 17, G-Eazy and Kehlani, "Good Life", from the soundtrack for The Fate of the Furious
- RONALD:”I look at you like a day one. Real talk.”2018 November 1, Ben Ketai, 23:00 from the start, in Start Up, season 3, episode 1, spoken by Ronald Dacey (Edi Gathegi)

day one

At the very beginning; when something is entirely new.
- to buy something day one

A very special thank-you to my brilliant band—especially my day ones, Jelly Bean Johnson and Monte Moir.2019, Morris Day, On Time: A Princely Life in Funk, Da Capo Press, →ISBN:
To my day ones: Jude Viaud, Roberto Franco, Antonio Wormley, and Jared Allen.2019, Keith Sarasin, Chris Viaud, Farmers Dinner Cookbook: A Story in Every Bite: A Story in Every Bite, Cider Mill Press, →ISBN, page 297:
Pistols was my dawg, my day one, my right hand, so I didn't ever want us to be out because of me not being able to keep my dick in my jeans.2019, Liv Reshelle, Dymond & Pistols: Forever & Always, Sullivan Group Publishing:

plural	day ones

What does day one mean?: Day one means the very beginning.
How do you use day one in a sentence?: A very special thank-you to my brilliant band—especially my day ones, Jelly Bean Johnson and Monte Moir.
What part of speech is day one?: Day one can be a noun or an adverb.
What is the plural of day one?: The plural of day one is day ones.

Adapted from Wiktionary: day one (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

Last updated: 2026-09-02

Cite this entry: “day one.” Word.ws, https://word.ws/day_one. Based on Wiktionary, CC BY-SA 4.0.