Final answer:
Professional duty begins as soon as the client enters into an express or implied therapeutic contract in the field of law.
Step-by-step explanation:
In the context of the question, the subject being discussed is related to law.
Professional duty begins as soon as the client enters into an express or implied therapeutic contract. An express contract is a clear and explicit agreement made between the client and the professional, where both parties explicitly state their rights and responsibilities. On the other hand, an implied contract is not explicitly stated but is inferred from the conduct and actions of the client and the professional.
For example, in the field of law, a lawyer's professional duty starts when they enter into an express or implied therapeutic contract with their client. This contract establishes the lawyer's obligation to provide competent and diligent representation to the client.