My friend in Busan was surprised that workers in US corporations refer to their managers by their first name. Not all all corporations, but many practice this informal style in America. While some workers will use "Mr./Miss/Mrs." as a title, and use their manager's last/family name (example" Mr. Smith), it's more common to hear subordinates refer to their managers by their first name only. It wasn't always this way, but I think the corporate environment in the US became more informal gradually over the past decades. 🤔 In schools, teachers are usually referred to in a formal tone (example: Mr. Smith or Professor Smith).