Some people will tell you the concept of "The One" is nonsense but I don't think it is. I think it's romantic and beautiful and if you believe in finding The One then good luck. I hope you do. I definitely do think there's an element of context and circumstance to finding The One. For instance, if you go to one college rather than another, The One might be someone in one universe and someone else in the parallel version. But the fact is, YOU only get to choose ONE path in this life, so why not go ahead with the belief that the person you choose to be The One is the actual One. It's lovely and comforting and special and there's not all that much other than love that we can really rely on to add a little bit of magic to existence. (Unless you include science because woah, that shit's pretty magical too. But I digress.)
For all the romantics out there (boo, cynics, boo!), deciding when someone is The One is a process that requires some head work as well as heart work. There are certain things you need to know about yourself, and the person you're in love with, before you can go ahead and call them The One. Because only fools rush in, right? And once you've chosen someone to be your One, you want to be right. No one wants to have to backtrack on calling their partner The One.
Here are the things you should know for sure before you call someone "The One":
1. That your future priorities match up
Love is as much about the head as it is the heart. Someone can seem like The One in your heart, but if your heads are at different places, it's likely that feeling won't last for long.
2. How they treat you when they're mad at you
The One will love you even when they're mad at you, and vise versa. If you've never fought or disagreed with someone, then be wary of calling them The One!
3. What you're looking for
Before you meet The One, you should have met at least a handful of Not The Ones. This is what helps you learn what it is you're looking for in another person. Having some experience is important (although our grandparents' generation might tell us otherwise) in order to figure out what it is you do and don't like in other people.
4. How committed you are to compromise and hard work
It's not all about the other person. YOU need to be ready and willing and eager to work hard and make compromises. Even though The One might seem "easy", The One is actually going to be the hardest one because it's real and it's forever.
5. How you feel about yourself and who you are
What Queen Ru said.
6. How you fare spending long periods of time together
If you've never spent more than a day and a night with someone, forget calling them The One. Until you've travelled or lived together, you'll never know if they're it or not. If you can still love someone after living in their farts for a week, then go ahead, by all means, call them The One. Because you're going to be living in those farts forever.
7. What you're both willing to do to make the relationship work
You should know the lengths you and your partner are willing to go to for one another before you settle on The One, because the effort you both put in should be equal (Which does not necessarily mean the same, people bring different things to the relationships, but they should bring things in equal measure).
8. How trustworthy they are
If you don't trust someone, they're not The One. Obviously, trust takes time to build, but if you can't get there, then hold off on your proclamations.
9. How many butterflies are in your tummy even after a long time of dating
The One should give you butterflies, even after years of living in a cloud of their farts. Maybe not butterflies every day, but they should always excite you to some extent, even if that excitement comes from just sitting next to one another in silence and reading.
10. How happy they make you
The One is not someone who makes you miserable all the time. Sure, there will be trying times with The One, but if the person you love makes you feel bad about yourself, is abusive in any way, or generally makes you miserable, then they should not be The One for you.
11. How much you can rely on them
The One should be someone who answers your calls, and when they can't, returns them as soon as possible. You should be able to rely on The One to always think about your interests when they're making life decisions. The One is the one who will be there for you when you really need it, unconditionally.