When it comes to girl world, there are about a million levels of friendship.

You’ve got your friend of a friend, the girl you met when you ran into one of your friends briefly, and now you give each other a nice smile when you see one another on campus.

Then there’s the friend. She’s a sweet girl, you have some stuff in common and will probably sit together in class, but that’s about as far as that friendship goes.

After her comes the ‘good friends.’ They might know who you like, you’ll probably pre-game together and you’ll text a couple times a week. You’re fairly close with them, but they don’t compare to the girl who comes next.

The end all be all, the girl you are sure you could not possibly live without, the one who knows everything about you and more, the girl who is your best friend.

So how exactly do you know when a girl has earned the title of ‘best friend?’

1. She is always there

This girl will be there for you whether it’s 3 a.m. or 3 p.m. –– it doesn’t matter. You can call, text or tweet her any hour of the day with a crisis, and she will be there for you without even questioning it. You can be a sobbing mess on the floor and she’ll stay with you until you’re not, all while spoon feeding you raw cookie dough.

2. She's never afraid to tell you if an outfit doesn't look cute

A good friend might be scared to be honest, but a best friend will be as blunt as humanly possible.That being said, a best friend will make sure to tell you nicely.

3. She knows you better than you do

You can try to lie to her, you can play it off like you’re not upset, but she will call you out on it in a heartbeat. The “I’m fine” excuse will never work on her so don't even try using it. She’ll come out with a whole list of reasons why she knows you’re full of it, then to top it off she’ll tell you exactly how you feel in that moment. You’ll sit there in shock because you didn’t even have to say anything, she just knew.

4. She hates someone more than you

If a boy hurts you, you can bet your best friend will hate him more than you. Even once you're over it, she will still glare at him every single time she sees him. If another girl hurts you? They are officially dead to your best friend. Your best friend understands the rules of girl code and will be loyal to you no matter what.

5. She is part of your family

Your siblings and probably even parents follow her on Instagram. They treat her like she’s one of their own. She can strut right into your house and feel totally at home. Family dinners are essentially incomplete without her. She is welcome at all events including, but not limited to, birthday dinners, anniversary parties and particularly horrendous family reunions.

6. She doesn't have any boundaries

Your best friend knows that no topic is off limits. There is absolutely nothing that you would hide from her. No matter how gross, personal or potentially inappropriate the story is, she will sit there and take in every word. No question goes unasked, no favor undone. You need to borrow underwear? Done. Need help tweezing your eyebrows? Done. Wants to know every detail of your date with that cute boy, and I mean every detail? Done.

7. She will always listen

Regardless of how big or small your latest life drama is, your best friend will listen. She will pay attention to every detail, and then offer you the finest advice because, after all, she’s gone through the exact same thing. She’ll tell you the boys will come and go, that your GPA does not mean you’re going to be homeless after graduation and that your hair is not that bad. You’ll go off for hours and she will listen, sporadically adding in words of wisdom, and she won’t mind one bit because she knows in 20 minutes, when you’re finally done talking, it’s her turn rant. And you’ll sit there and listen to every word she has to say, and you’ll offer up your own advice because that’s just what best friends do.

8. She would never hurt you on purpose

A best friend would never go out of their way to say something mean. She would never want to hurt your feelings or upset you. And if by some strange and sad turn of events, you get into a fight, a best friend will always be willing to talk it out. A best friend will not keep a grudge; once the fight has been solved and all is forgiven, she will let it go. Besides, you can't stay mad at each other that long because there are too many funny Instagrams to tag her in.

9. She doesn’t care how weird you are

You could be the weirdest person in the world, but your best friend won’t care. In fact, she’ll be right there beside you being just as weird –– if not weirder. You can say dumb things or dance like a fool in your room, and she won't even think about it twice. When you snort laugh or spit out your water when she makes a joke, she’ll double over in laughter without a trace of judgment. If you listen to Hannah Montana, she’ll sing every word with you. If you spend hours watching make-up tutorials and make yourself look like a Kardashian had a baby with a clown, she’ll still let you practice on her. Because at the end of the day, she loves you no matter what, weird quirks and all.

10. She has everything and nothing in common with you

While you and your best friend are convinced you are the same person separated at birth, you also know you could not be more different. Both of you know that’s exactly what makes your friendship work. All of your similarities are balanced out by your differences.

Go tell your best friend you love her, give her a hug and thank her for putting up with you no matter what.