What does "Re:" in a business letter mean? When should we use it?


Wiktionary lists re as a preposition that means “About, regarding, with reference to; especially in letters and documents”, while OED1 (1914) says:

Re sb² [Ablative of L. res thing, affair.] In the matter of, referring to. The L. phr. in re is similarly used († formerly also = in reality). Re infecta, ‘with the matter unfinished or unaccomplished’, has also been freq. employed in Eng.

Thus, use of re as a preposition meaning about or regarding seems perfectly reasonable to me; it's a concise alternative to regarding, a word which is often used verbosely.

Use re when introducing a new topic. For example, the following would be grammatically and perhaps even stylistically acceptable:

Re item 1, she has no opinion. Re item 2, he doesn't like it. Re item 3, they are sick of it.

Alternative forms of that, with fewer instances of re, might be:

She has no opinion re item 1. He doesn't like item 2. They are sick of item 3.
She has no opinion about item 1. He doesn't like item 2. They are sick of item 3.

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    As an aside, sb (substantive) in the OED1 corresponds to n (noun) in the OED2 and later. The OED2 still categorizes re as a noun, but it adds: "Now freq. apprehended as a preposition, and used in weakened senses to mean 'about, concerning'." The OED2 also noted: "The use as a preposition has freq. been condemned: see Fowler Mod. Eng. Usage (1926) [...]". Later, they noted the form re. (with period), saying that it "probably results from reanalysis as showing an abbreviation for 'regarding'", and I think that's what it is now for many speakers; re has come a long way since 1914. – snailplane Nov 17 '13 at 22:52

RE or Re is just a prefix used before the subject line of a previous email message to mean the new message is a reply for a previous message.
In a business letter, it introduces the subject that it is about.

Re your letter of August 2

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    Re is most commonly used that way, but it also occasionally appears in the middle of messages, and even in the middle of sentences--sometimes even in speech! Collins gives "he spoke to me re your complaint" as an example. (I'm not sure I would encourage the OP to use it in the manner I'm describing here, but it's probably common enough to be worth understanding.) – snailplane Nov 17 '13 at 15:07
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    @snailboat: Agreed. There's an increasing tendency to use "re" as a direct replacement for "regarding, about, on the matter of", but outside of "auto-generated email header" contexts (or manual replication of same) it's probably a bit too casual for many contexts. My advice to learners would be "accept it when used by others, but don't try to extend the usage beyond introductory heading contexts yourself". – FumbleFingers Reinstate Monica Nov 17 '13 at 16:02
  • @FumbleFingers Your point about not actually recommend its usage is very important. While its easily understood, it really does seem too casual to be considered "neutral" level formality. To me it feels like the writer couldn't be bothered to write out the word "regarding" in full (even though that's not technically its origin). – Kit Johnson Mar 7 '17 at 5:03

RE: Stands for regarding to/or Referring to when used in a business letter (equivalent to Subject line in emails). Was often used in business letters before emails were popular, hence the confusion.
Used as a subject first line of the letter and not in the main text. Example, right before or after salutation:

RE: TAX payments

To whom it may concern,

I have been informed.....(Main text of first paragraph)


Dear MR/MRS X,

RE: Open job position for Arts consultant

I am interested in applying for the above mentioned opening ......(Main text of first paragraph)

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