shy

Being shy means feeling nervous or uncomfortable around other people, often because you don't like being the center of attention.

When we say someone's shy, it usually means they get quiet and awkward when they have to talk to a lot of people at once. They might avoid eye contact or not want to be in big groups, even if they're really nice one-on-one. It's like their personality gets hidden behind a layer of shyness when there are too many other people around. But that doesn't mean they're not friendly or interesting - it just takes them a little while to warm up and feel comfortable.