When it comes to your sister, you've mastered the art of gift giving. You always end up winning the prize of best present for your her birthday and every holiday. You just can't help it if you spot something from a mile away that just screams your sister's taste the minute you walk into a store.

When it's time to choose the perfect movie to watch for girls' night in with your sis, there's no question about it. You already know you're watching your favorite rom-com. You'll also be quoting it to each other the whole time, so sorry in advance to anyone else who has to watch it with you.

You can tell when your sister is hungry even before her stomach begins to growl. That's when you know exactly where to go: her favorite restaurant. It may not be your first choice, but you know it'll make your sister happy.

No matter what time it is, your sister always makes herself available to chat. Even if it's super late, you know she'll answer her phone, because she's your person and emergency contact. (Thank you very much, Grey's Anatomy.)

There's an unwritten rule for sisters: what's yours is mine. So, you already know that when your favorite oversized sweater is missing from your closet, it's probably because your sister is either wearing it or has it stashed in her closet. You're so used to sharing by now that you don't even need to ask.

Anytime you get nostalgic AF, you can run to your sis to remember the good old days. That's usually when you end up retelling old stories of times when your parents did something downright hilarious. You don't even need to ask her if she remembers, because she's jumping in and filling in all the gaps with the best details.

Along with being able to share, sisters are pros at keeping each other's secrets. There are some secrets I've kept for my sister for decades, and they're not going anywhere. Sisterly secrets are locked away forever in the tightest of vaults that no one else could ever crack — believe me.

The minute you see your sis, you can tell what kind of day she had. So, if she looks a little down in the dumps, you don't even need to ask. Instead, you race to the kitchen to grab her favorite snack and pour two glasses of wine, and are ready for the vent session.

You don't need to ask what your sis's most embarrassing story is, because you were likely there to experience it right there with her. It might be your most embarrassing story, too, or it's your favorite memory to retell. As humiliating as it was at the time, by now, it's the one story that's guaranteed to make you both cry laughing every time you remember it.

Sisters can read each other's mind with just one look. It's how you communicate when you're at the Thanksgiving dinner table and your aunt makes an eye-roll-worthy comment.

With just one look, you and your sis can also ask each other, "Did you just see what I just saw?!" Instead of vocally confirming, that subtle look lets you know, "Yes," and it makes you laugh.