Which term refers to a skilled practitioner who is effective, organized, competent, and businesslike?

The term "Professional" refers to someone who has extensive knowledge and skills in a particular field and demonstrates a high level of competence and expertise. A professional typically exhibits qualities such as effectiveness in their task execution, organization in their work approach, and a businesslike demeanor, which includes reliability and ethical behavior. This term conveys not just capability, but also a commitment to excellence and continual development within their profession.

The other terms listed do not convey the same level of skill and competence. An amateur generally lacks the expertise and proficiency that professionals possess, while a novice is someone who is just beginning to learn and lacks experience. An assistant, on the other hand, typically supports professionals rather than embodying the characteristics of competence and effectiveness that define a professional.