The Meaning of RE: in Emails

RE: has different definitions in paper and electronic communications

Close-Up Of Fountain Pen On Paper

Matteo Reggiani / Getty Images

Back when written messages were commonly delivered on paper, the term Re stood for "regarding," or "in reference to." It was used at the top of a formal letter, followed by the subject of the letter. Re isn't an abbreviation. Rather, it's taken from the Latin in re which means "in the matter of."

With the advent of electronic communications, however, the use of RE: has taken on a repurposed meaning. RE: in an email subject line precedes the subject when the message is a reply to a previous one that uses the same subject.

This indicator helps you and your correspondents recognize messages and responses that are on a particular topic, which is especially helpful if you're engaged in multiple email conversations at the same time. 

When RE: Causes Confusion in Emails

RE: is typically added in front of the subject of a reply email automatically. However, if you put it there manually in a new message, meaning to indicate "regarding," recipients may be confused. They may think the message is a reply that belongs to an email thread they haven't seen. Regardless of what might be true in other contexts, in email correspondence RE: or Re: doesn't mean "regarding." It means "reply."

Use RE: For Reply

To prevent confusion, don't insert RE: in a subject line. The fact of the subject line itself implies that this is what the message is "regarding." Instead, allow RE: to appear when you reply to an email message sent to you.