expert

Carries a connotation of authority and mastery. It implies not just knowledge, but the ability to apply that knowledge with precision and confidence. While a 'specialist' might have narrow focus, an 'expert' is perceived as having reached a peak level of proficiency. In professional contexts, it suggests a level of skill that warrants trust or payment for consultation. It is generally positive, though in casual conversation, calling someone an "expert" can occasionally be used sarcastically to mock someone who thinks they know more than they actually do. When used as an adjective, it describes the quality of the action itself (e.g., 'expert timing'), shifting the focus from the person's credentials to the flawless execution of the task.