Meaning of RE in English

I .

/ reɪ; NAmE /

= ray (4)

II .

/ riː; NAmE / preposition

used at the beginning of a business letter, etc. to introduce the subject that it is about; used on an email that you are sending as a reply :

Re your letter of 1 September ...

Re: travel expenses



II . Latin , ablative of res thing.

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.