Sonny is an informal, friendly way to address a boy or young man, often used by someone older. When a grandfather calls his grandson “sonny,” or when a police officer says “Where are you headed, sonny?” to a teenager, they're using it as a casual term of address rather than the person's actual name.

The word carries a warm, affectionate tone when used by family members or friendly adults. A shopkeeper might say “Can I help you find something, sonny?” to a young customer. However, the tone matters: sometimes adults use it in a slightly condescending way, like when someone says “Listen here, sonny” before giving unsolicited advice.

You'll often encounter sonny in older books and movies, where it was more commonly used. Today it sounds a bit old-fashioned, though grandparents and older relatives still use it naturally. You don't have to be someone's actual son to be called sonny. It's simply a way of acknowledging someone's youth, similar to how “kiddo” or “young man” might be used today.