When speaking with my mother a couple of days ago, I read to her a message I was sending to my cousin on her behalf ending with: "... the birthday of your youngest." [implying her child]

She immediately leapt on this and said that as my cousin only had two children, the use of the superlative was not permitted and the comparative must be used instead: "... the birthday of your younger child."

She was adamant that this was a solid grammatical rule that she was taught throughout her education. As a younger Briton, I have relatively little formal grammatical education to older people who were better taught in this regard, so I usually defer to her on grammatical rule knowledge.

Is she right? Are superlatives not permitted when the domain of the object is only two?

To me it seems bizarre. The minimum or maximum of any set does not only exist when there are different minima and maxima, or indeed something which is neither.

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    Ignoring the actual question for a moment, I will say that whenever I find myself in a similar situation, I try not to forget the "on her behalf" part. After all, if someone were writing a letter on my behalf, I would most probably insist on all kinds of things, too. – RegDwigнt Nov 27 '10 at 4:41
  • @RegDwight Granted. This was a far less formal arrangement and was actually a text message. But I have never seen the need to slack on grammar because of a poorly used medium! – Orbling Nov 27 '10 at 11:50
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    It's not a hard and fast rule. If you were talking about the 10th plague of Moses, if you said "the death of the oldest, older, or only son in every family," you would sound ridiculous. On the other hand, if you ask "Which of the two is oldest?" I think there are good grounds for saying this is incorrect. – Peter Shor Jun 11 '11 at 13:00
  • @Peter Shor: What are the grounds? Is it just an arbitrary rule, or is there some good reason for using '... is the older?' rather than '... is oldest?' – Orbling Jun 11 '11 at 14:48
  • It just sounds wrong to me, so yes, an arbitrary rule. But if you have two children, saying "this is my oldest" sounds fine to me (and "this is my older" sounds funny - you would need to use "older child"). – Peter Shor Jun 11 '11 at 16:18

It certainly used to be a rule, but there are grounds for ignoring it. This would be strongest where you were uncertain of the number of children (not the case here). But you can certainly argue that in logic, there is an oldest of 1, 2, or more children. So, your mother is almost certainly correct about what she was taught. Whether that stricture still has to be followed is considerably more debatable.

  • What is the basis of this rule? Just something some grammar teachers thought up to antagonize students? – Mr. Shiny and New 安宇 Nov 27 '10 at 4:42
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    Well it is the existence of the rule I am wondering about. You say there "certainly used to be a rule", when did it come in, or perhaps more importantly, has it ever gone out? – Orbling Nov 27 '10 at 11:54
  • I suspect the reason is brevity. If you can add meaning without adding words then there's often a rule that you should... unless you are deliberately trying to convey less. "my younger child" tells you how many children I have, "my youngest child" does not. – Philip Couling Aug 21 '18 at 14:54

No, she isn't right. The younger of two children is also the youngest. (Of course, both are correct, so if she prefers "younger" in her own letter, that's perfectly reasonable.) Indeed, there's a joke about referring to the only member of some category with a superlative (the joke being that the sole member is both the most X of its type and the least X of its type).

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    An only child is both the youngest and the oldest, sure. But you cannot say "the youngest of the two children", now can you? You would never ask someone which of their parents was the oldest. It just doesn’t feel right. The older parent is older than the other, since you can’t say that the oldest parent (of the two) is *oldest than the other. – tchrist Feb 23 '12 at 2:24
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    @tchrist: Yes, I can say "the youngest of the two". I usually wouldn't, because "the younger of the two" is more narrowly tailored, and we usually prefer that, but there are circumstances where youngest would be appropriate. For instance, for the sake of parallelism: "My father is the youngest of three children, and my mother is the youngest of two." (Google will also give you some quotes from Jane Austin and Shakespeare which use youngest of two rather casually, suggesting it used to be even more common.) – Henry Feb 23 '12 at 16:17

Some prescriptive style guides insist that the superlative can only be used when comparing three or more things, and that the comparative must be used when comparing only two things. If you are writing in a very formal situation, you may want to follow this rule.

However, in practice people often use the superlative for comparisons between only two items. This use of the superlative is completely acceptable in speech and may be used in writing for most audiences.

  • What if the number of things is uncertain in formal text? – xuhdev Feb 23 '17 at 10:02

I had never heard of this rule before reading your question! It's quite fascinating ...

To my ears, the superlative sounds awkward when used to pick out one member of a group which is generally understood, or explicitly given, to consist of two members. For example, all of the following sound odd to me:

  • my oldest parent
  • his left nostril is smallest
  • the youngest twin
  • the smartest of the two

The oddity of the above suggests that there is something to what your mother says. I would say that if it is known that there are exactly two members of the relevant group, it is more natural to use a comparative.

On a side note, quite a number of languages pattern the same way, so it is clearly not an idiosyncrasy of prescriptive English; rather, it might (might!) be a universal component of the meaning of superlatives.

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    Strange, none of those examples sound at all odd to me. It must vary by area and demographic. – Orbling Jun 12 '11 at 0:30
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    It'd be interesting to do a study to see if does correlate to social factors. I'll have to ask around to see if anyone's done any research. – jyc23 Jun 12 '11 at 1:49
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    Yes, those aren’t something I could generate. They sound bizarre. – tchrist Feb 23 '12 at 2:27

Yes, she is definitely correct. If you have two children you refer them to 'my elder' and 'my younger'. If you have more than two children you can say 'my eldest child' for no.1 or 'my youngest son' for no.3. Nowadays it seems only the second language English speakers have a chance to learn English grammar properly and rules of grammar in the native English speaking countries have been forgotten. When you have two plans you would say plan A is better than plan B. If you have three plans, you could say plan C is good, plan B is better (as compared to C only) and plan A is the best (among the three plans). the same goes with young, the younger and the youngest. However, it depends on how English exam boards view it. They can stick to the original rules or they want the world to use them differently, in other words, making them easier.

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    Well here you are quoting a rule, but what is the reason behind it. Logically, there is a youngest of two children, so why would this use be banned in speech? – Orbling Jun 11 '11 at 9:32
  • @Orbling No, you don’t get it. Logically there is not a “youngest of two” anything. You just can’t do that. – tchrist Feb 23 '12 at 2:28
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    @tchrist What does 'logically' mean here? Are you telling me that if John is 5ft tall and Bill is 6ft tall, Bill is not the tallest of the two by logic? You may not like the sentence, but there is no coherent semantics for the superlative that would make it false in this situation, which is what it would have to be if this were a matter of logic and not prescriptive grammar. – Alan Munn Feb 23 '12 at 2:57
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    So you don't say "Put your best foot forward" either, I guess. I'm not taking issue with your judgement per se, just the claim that there's any logic involved in it. And the connection to natural duals is an interesting one. I don't think it actually extends to superlatives, though. – Alan Munn Feb 23 '12 at 4:55
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    As I said, the observation is interesting, and you've described it very coherently. But then you don't help things by using the term 'logical' here. The fact that there are linguistic generalizations and perhaps even linguistic universals, doesn't make them logical without changing what you mean by 'logical' (as you explicitly say by switching to "human logic"). Let's keep logical with it's regular meaning and then discuss whether there's an empirical basis to the linguistic generalization. – Alan Munn Feb 23 '12 at 5:09

I agree that your mother is definitely correct. This cropped up in conversation recently when I was discussing my younger son (of two children) getting married. My learned friends all concurred that if you have two children you refer them to 'my elder' and 'my younger'. If you have more than two children you can say 'my eldest child' for no.1 or 'my youngest son' for no.3.


My 1st born son is getting married. He has a brother and a sister. In my invitation card I put "elder son" but all my friends I talked to about this issue of elder vs eldest say that it should be eldest son. I just don't get the grammar of that but nonetheless use it as I have never seen anyone in their wedding invitation ever use elder/younger but always eldest/youngest. My brother in law explained to me that it's not about comparison here but rather on ranking so I see it as saying "my eldest child, a son" which makes more sense but defies how I was taught English.

protected by tchrist Jun 5 '14 at 15:58

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