1) If the term "vocabulary" has been registered as a trademark, trademark infringement and unfair competition should be established. If not, it does not necessarily constitute an infringement (it can only be said that it is not necessarily an infringement, it depends on whether the influence of the term is well-known)

2) If it is suspected of infringement, then change the name, the most practical way .

3) If you don’t produce products, how can you register a trademark? If you are purely trying to protect your website, then registering a global domain name is already a protection.

4) None of them.