Maintain consistency with the vocabulary of the problem domain. Where necessary, clarify the users' terminology. But use their vocabulary as much as possible. This will prevent the common problem where the analysts and users spend their time reconciling two sets of terminology and arguing over interpretation.
When you remain faithful to the users' vocabulary, you will see the users take ownership of the models more quickly. Your questions will demonstrate your desire to understand the users and their needs. This show of respect draws the users into the project and improves your chances of success dramatically.