"Sup" is a casual greeting often used in informal conversations. It is a shortened form of "What's up?" and is commonly used among friends or peers to ask how someone is doing or what they are up to. This greeting is popular in various cultures, especially among younger people. The term "sup" can also be used in text messages and social media, making it a versatile way to initiate a conversation. It reflects a relaxed and friendly tone, encouraging open communication. Similar informal greetings include hey, hi, and what's good.