Bestie implies a deep bond, often used among younger people. It may sound too casual in formal contexts. Can't wait to catch up with my bestie this weekend!
Pro Tip 2/3
Emotional Connection
'Bestie' conveys affection and implies a lot of trust and shared experiences. My bestie and I can talk about anything.
Pro Tip 3/3
Gender Neutral
The term 'bestie' is gender-neutral and can refer to a close friend of any gender. John is my bestie, we've known each other since childhood.