You can have the biggest apartment or the fastest motorcycle in Paris, but if you're all alone, it won't be much fun. That's why there's l'amitié, which means "friendship" in English.
L'amitié makes parties more fun, brunch more delicious, and hard times easier to endure. The only true downside: It can also make you more broke, especially if your meilleure amie (best friend) convinces you these Stella McCartney shoes are impossible to live without.
(Of course, if they'll share their last squeeze of Beauty Flash Balm with you, then they definitely pass the friendship test...)
One more thing: If you're writing a letter in French, you can sign it amitiés, which roughly translates to "your friend" or "best wishes." But we prefer bisous!