“当教授”常见的英文表达有 “become a professor” 或 “serve as a professor”。
become a professor 强调从其他身份转变为教授这一职业身份的过程，例如： He dreamed of becoming a professor since he was a child. （他从小就梦想成为一名教授。）
serve as a professor 更侧重于描述当下正在担任教授这一职位履行职责的状态 ，例如： She will serve as a professor at this university next year. （她明年将在这所大学担任教授。）