Day One

What does day one mean?

A very close friend

A "day one" is a person you have been close with for a long time, whether it be platonically or romantically. You have been with them since day one (since you were a kid or you have been close since meeting for the first time) and have experienced a lot of bad and good times together.

Where does "day one" come from?

The general "day one" phrase has been around for many years and was/is primarily used to describe the beginnings of something, whether it be the start of a relationship or a job. But the origins of this specific iteration of "day one" as a noun to refer to a BFF date approximately to the mid-2010s. It has since grown as an alternative to bae and bestie to separate the best partners from the chaff.

Where would I see "day one" used?

You may hear "day one" used in person or see it used in texts or online, especially on social sites, like Twitter, Instagram, and TikTok. When used on social media it's typically seen in some type of tribute post thanking a close friend for being with them through thick and thin.

Who uses "day one"?

Close friends are the ones that most often use the term as a substitute for the "best friend" label to express their love and appreciation for each other. Some examples include lifelong friends since grade school or a couple that met in their early 20s and has been married for 50 years.


I just wanna say thanks for being my day one. I couldn't have done this without you. I love you!

Causing trouble with their day one

Related Slang


Updated January 4, 2022

Day one definition by

This page explains what the slang term "Day one" means. The definition, example, and related terms listed above have been written and compiled by the team.

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