Non-PRO English to Japanese Law/Patents Law (general) 米国の法主体

These terms appear in the list of entities in a document related to U. S. federal taxation. Ｉ know the meaning of each word, i.e., Trust is 「信託」, Nominee is 「名義人」, EIN is 「雇用者番号」 and SSN is 「社会保障番号」, but I have no idea what these terms mean.

I appreciate any help.