1. You speak to each other in an intricately crafted dialect of gibberish that nobody else understands.
2. You feel entirely comfortable climbing into their bed at 4 a.m. Uninvited.
3. They are privy to your secret prejudices. They still love you, somehow.
4. They “like” your Facebook updates, Instagrams, and tweets as soon as they go up.
5. You indulge in all of your guilty pleasures together, and have a mutual agreement to keep your uncoolness secret.
6. You’ve started mentally collecting anecdotes for your Maid of Honor/Best Man speech.
7. You literally always owe each other money but trust that you’ll balance out over the years.
8. You reserve your most colorful and most vulgar insults for one another.
9. You know their wardrobe inside-out.
10. You keep each other updated on your bodily functions. Maybe too vividly.
11. You can sense each other’s emotional state over text message, based on punctuation and Emoji usage.
12. You’re Facebook friends with each other’s parents, siblings, and significant others.
13. You’ve traveled with each other for an extended period of time without ending up wanting to kill each other.
14. You hate all the same people, no questions asked.
15. You can discuss the following things freely: money, sex, religion, family.
16. You’ve stopped feeling the need to wear pants around each other.
17. Your Snapchats to each other prove that the human face is capable of some remarkably unflattering contortions.
18. Despite being intelligent as individuals, you’re truly harebrained collectively.
19. You know each other’s preferred drinks and you’ve gotten really good at making them.
20. You have each other’s romantic histories memorized, including heroes, villains, and even the briefest cameos.
21. You had a specific memory in mind for every single item on this list.
22. And you’re gonna spend the next 20 minutes on the phone with your BFF, checking them all off.