Can I have a contact connected to more than one account?

An account can have multiple contacts, but a contact cannot have multiple accounts.

Why?

This is because an account is a more general entity than a contact. 

For example, an optical store would be considered an account that can have multiple contacts such as employees or decision makers. 

Therefore, a contact is linked to a single account, while an account can have multiple contacts.

You can thus create an account that will have multiple contacts (multiple sellers for a single store) but not the other way around.