Lynne Truss (yes, she of Eats, Shoots and Leaves fame) refers to a number of definitions: âPunctuation marks are the traffic signals of language: they tell us to slow down, notice this, take a detour and stop.â And âPunctuation is a courtesy designed to help readers to understand a story without stumbling.â Quoted from http://www.dorisandbertie.com/goodcopybadcopy/2009/09/08/punctuation-why-do-we-need-it-anyway/ Thatâs about the written word but we should be aware of the connection between speech and writing.  Sharon, if Iâm not mistaken, you would agree that we are concerned with imposing grammatical categories and punctuation rules on the written representation of spoken sentences, so that a text can be successfully decoded by the inner ear and ultimately given meaning by the brain. There is a âruleâ that the relative pronoun can be omitted from a defining relative clause but must be retained in a non-defining one. I use the following example in class:     The students who lived in Haifa left early.   v   The students, who lived in Haifa, left early. In the first, a definingrelative clause, some of the students did not live in Haifa and in addition only they did not leave early. In the second, a non-defining relative, all the students lived in Haifa and all left early.  Furthermore, true to the rule, the second sentence would be ungrammatical without the relative:                                                            * The students, lived in Haifa, left early. In your van example, however, as you point out, something sounds amiss.  "The van which I bought three weeks ago already needs repairs" can be shortened to "The van I bought three weeks ago already needs repairs" without any apparent loss or change in meaning. This puts it clearly in the defining category. So how can it be acceptable if we only haveone van? A lot depends on your intonation, as you suggest. Iâm trying to place your original verbal utterance in a context which I think most English speakers and teachers would find perfectly natural. You bought a van three weeks ago and it is already in need of repair. You have no other van. You tell someone about the problem of its needing repair, probably in a complaining voice. He/she probably already knows that you bought a van recently but you use a relative clause to emphasise the recentness of the purchase and to remind them of it. We do often seem to define things and people as a sort of memory jog. âYou remember my van? You know I told you I bought a van three weeks ago.â In your sentence the relative clause seems to modify âvanâ rather like an adjective before a noun when no defining is involved. If I say âWe bought a red sofaâ the word red describes sofa. âThey repaired my three-week old vanâ does not imply that I have other vans unless you use marked intonation. In addition, it seems that there is an element of ambiguity in the use of the relative clause as the interlocutor may or may not take it as a definition, depending on whether he/she remembers.  Does this help? That was just some brainstorming and Iâm sure thereâs lot more to it. Joe Barnett  On Friday, November 1, 2013 9:48 AM, ETNI list <etni.list@xxxxxxxxx> wrote: ---------- Forwarded message ---------- From: Sharon Tzur <sharontzu5@xxxxxxxxx> Subject: Defining and non-defining "Can it be said that the same defining relative clause can be also be non-defining, depending on the context. For example, "The van which I bought three weeks ago already needs repairs" sounds more like non defining to me." My opinion: if you have several vans, then the clause is defining because you are explaining which of the vans you are talking about. If you just have one van..then the clause is non-defining. Use punctuation to make the distinction. If it is non-defining, then the relative clause must be preceded and followed by commas. Some purists prefer to use "that" for defining clauses. What about this "A few friends whom I met at the new school are coming to the party"? My opinion: I'm not as sure on this one...I think it sounds like non-defining...perhaps because I'm bothered by "a few" if used as defining, but I can't explain why it doesn't ring right to me. For a defining clause I׳d prefer, "The friends that I met at the new school are coming to the party." You have many friends and are defining which of them you are talking about. If it is non defining, it sounds as if those few friends are the only ones coming to the party. To teach the distinction, I use the following: Teachers that work hard should be well paid. Teachers, who work hard, should be well paid. In sentence one you define which teachers should be well paid. In sentence two, you are saying that all teachers should be well paid, and adding a comment that they all work hard. Yours, Sharon Tzur ************************************** ** Join ETNI on Facebook  https://www.facebook.com/groups/31737970668/ ** ETNI Blog and Poll  http://ask-etni.blogspot.co.il/ ** Etni homepage - http://www.etni.org ** post to ETNI List - etni@xxxxxxxxxxxxx ** help - ask@xxxxxxxx *************************************** ************************************** ** Join ETNI on Facebook https://www.facebook.com/groups/31737970668/ ** ETNI Blog and Poll http://ask-etni.blogspot.co.il/ ** Etni homepage - http://www.etni.org ** post to ETNI List - etni@xxxxxxxxxxxxx ** help - ask@xxxxxxxx ***************************************