Re may refer to any of the following:
1. Re is a word from the Latin noun "res" for thing, re is in reference to; regarding; concerning.
2. In e-mail RE: in the subject line is short for reply. When composing a new e-mail you should not place Re: in front of the subject, allow the e-mail program to create the Re: for you when replying to an e-mail message.
3. RE is an acronym for regular expression.
4. .re is the top level domain for the country code Reunion.
5. Re is chat slang for regarding.