What is your major?

Professional: this is an adjective, and the noun form is professional, which means major in university.

Translation 2: What is your major?

Or: What's your major?

Major: it means major; Specialized courses.

Example:

1.？ His major in university is international trade. ?

He majored in international business at the university.

2. Professional assistants are part-time employees who are trained to help professionals?

A trained staff member who is not a member of a specific occupation but helps a professional.

3. Medical skill, medical occupation, medical technology and specialty?

The art or profession of medicine.

Someone who does something, especially a profession, profession or technology?

One who does something, especially a profession, profession, or technology.