This question is related to this other one, about the difference between Phonetics and Phonology.

I can understand the difference between the two subfields as well as what it means to produce phonetic and phonologic transcriptions. Simply stated, the phonetic transcription deals with the surface representation, whereas the phonemic one deals with the underlying representation. But how does one determine what is the underlying representation? For example, in English, [r] and [ɹ] are considered variants (or allophones) of the phoneme /r/. But what is so special about /r/? Why can't we say that these two sounds are variants of the phoneme /ɹ/, instead? Of course, this is just one example. It can be extrapolated to any pair of allophones, such as [p] versus [b] in Korean or [d] versus [ð] in Spanish, etc.

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    My guess is that it is more or less arbitrary, based on tradition/convention. The symbols with less variants are probably older: Sir William Jones probably didn't use phonetic symbols, but described only phonology in more or less standard letters.
    – Cerberus
    Commented Sep 21, 2011 at 1:19
  • I don't think it's entirely arbitrary. Consider an [s] vs [z] alternation, the latter occurring intervocalically. An underlying /s/ that is voiced intervocalically seems more plausible than an underlying /z/ that is unvoiced when not intervocalic. Commented Sep 21, 2011 at 2:08
  • @JamesTauber: Fair enough, the symbols were chosen based on usefulness, not just at random. Your example suggests that the choice for s was based on phonological history (or frequency?), which seems a good argument. But that only works if the allophones have each a real letter that is actually used to distinguish them (z v. s); in the case of r, that is not the case, and so it was probably chosen because it is a real letter used in real words that contain the allophones. (Perhaps I am missing some of the subtler points of phonetics.)
    – Cerberus
    Commented Sep 21, 2011 at 3:03
  • Your question title is asking about phonemes and allophones but your question body and some of the answers seem to be dealing instead with the choice of symbols used for transcription, which is not the same thing at all. Please clarify your question. Commented Sep 21, 2011 at 8:31
  • @hippietrail I'm not so much concerned with the symbols as with which of the allophones themselves gets to be chosen as "the phoneme". If the symbol /r/ is used instead of /ɹ/, this is just an indication that the allophone [r] was chosen as a sort of representative of its class (if this assumption is wrong, someone please correct me). The question, therefore, is: why was [r] chosen? Now, once one of them has been elected (whatever the reason) the phoneme symbol can be straightforwardly derived, by replacing brackets with slashes. Commented Sep 21, 2011 at 13:02

3 Answers 3


You're absolutely right - the choice is completely arbitrary. Generally, before the publication of The Sound Pattern of English (Chomsky & Halley 1968), whichever underlying representation required the fewest number of rule derivations to produce the output forms was chosen, i.e., whichever was the most elegant.

For example, the following rule set describing (simplified) Korean stop allophony:

/p/ -> [b] / V_V
/p/ -> [p] / otherwise

Would be preferable to:

/b/ -> [p] / #_
/b/ -> [p] / _#
/b/ -> [b] / otherwise

Post-SPE, sound segments were reanalyzed as bundles of features - for example, [p] is shorthand for:


In SPE phonology, all features in the phonetic form of a segment are specified. However, the phonemic form omits features that are derived through rules - this is known as underspecification. For example, in SPE phonology:

[ labial      -> [+voiced] / [+voiced] _ [+voiced]

Note that only the modified features are written after the -> arrow, and that only relevant features in the surrounding environment are written after the /, rather than whole feature sets.

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    So the choice is not completely arbitrary, it can be motivated on grounds of elegance, simplicity, etc. Commented Sep 21, 2011 at 2:14
  • 2
    Without psychological evidence of some sort, I see no reason the human language faculty would consider one analysis as "simpler" than another.
    – Alek Storm
    Commented Sep 21, 2011 at 2:33
  • 2
    I agree with you, but it still isn't "arbitrary" if there's a criterion for choosing between two analyzes (even if not psychologically motivated) Commented Sep 21, 2011 at 2:54
  • 1
    Okay, perhaps I should qualify the word "arbitrary" somehow. How about changing "completely" to "empirically" in the opening line?
    – Alek Storm
    Commented Sep 21, 2011 at 2:58

@AlekStorm's answer is pretty good, but I'd say that in practice there are at least two ways linguists decide which form is underlying.

1) If you take two allophones, say (using relatively broad transcription) [t] and [ɾ]. You could, rather tediously, list all the contexts where [t] shows up, and all the contexts where [ɾ] shows up. Then, you can so some set operations. Call T the set where [t] shows up and D the context where [ɾ] shows up. It should be the case that T-D is a relatively small set of contexts, and D-T should be empty. In this case, [ɾ] has a restricted distribution, so the features of [t] could be considered underlying. This is similar to the elegance of description from @AlekStom's answer. Of course, in practice it will happen that neither A-B nor B-A is empty, and then everything gets more complicated.

2) You can check to see if one allophone "behaves" as if it were the other. As with [t] and [ɾ], the diagnostic would be

  • Does [t] ever behave as if it were a voiced, lenis segment?
  • Does [ɾ] ever behave as if it were a voiceless segment?

In fact, in many dialects [ɾ] does frequently behave as a voiceless segment, triggering changes in quality of its preceding vowel. For example, in Canadian English and some other dialects, there is the following distinction between write and ride.

raɪd   (ride)
rʌɪt   (write)

When adding on the morpheme -er, the /t/ in writer is flapped.

raɪɾɚ   (rider)
rʌɪɾɚ   (writer)

This case has the additional complication that both the [d] and the [t] are neutralized to [ɾ]. However, you could still argue that the vowel difference between [aɪ] and [ʌi] is triggered by voicelessness, so that the underlying form of the [ɾ] in writer is behaving as a voiceless segment.

But, like I said, heuristics like these are not applicable to all analyses, and there are certainly underlying forms which have been posited on flimsy evidence. And thank god, because that means that linguists' work is not done!

  • Could you give an example of [ɾ] behaving as a voiceless segment? Commented Sep 21, 2011 at 16:16
  • I added an example in.
    – JoFrhwld
    Commented Sep 21, 2011 at 19:36
  • Another example is the tendency to shorten the vowel preceding a voiceless coda in AmE. Commented Sep 20, 2012 at 23:46

It's not arbitrary, and while the ease of rule-writing is certainly a consideration, this is not what determines which sound is the phoneme and which sound is the allophone. To re-use @Alek Storm's first example:

/p/ -> [b] / V_V

/p/ -> [p] / otherwise

It's true that this is a simpler analysis than trying to instead account for [b] becoming [p] in a wide range of environments. But, the actual reason why [b] is a variant of [p] is because [p] can occur anywhere, while [b] can only occur in a specific phonetic environment. That is, the voiceless bilabial plosive only becomes voiced when it occurs inter-vocalically, because the voicing of the surrounding vowels carries across to the otherwise voiceless plosive. So, when you start to find phones which seem to be variants of the same sound, you need to look at the environments they occur in to work out which phones have plausibly been affected by the surrounding phones, and which phones seem to be robust in a range of environments.

That said, there are languages which permit a lot of 'free variation' (allophones that don't seem to arise through phonetic conditioning), in which case linguists might choose 'the phoneme' based on frequency, ease of explanation, or familiarity with one type of sound over another. But, in many analyses noting 'free variation', there do turn out to be phonetic factors governing the variation.

  • All phonetic environments are specific, because there is only a finite amount of possible combinations of segments in a given language. I could make an equally strong argument, based on phonetic factors, that the phoneme is underlyingly /b/, and is devoiced word-marginally (cf. German word-final devoicing and English word-initial aspiration) and next to voiceless obstruents due to the difficulty of maintaining voicing through the cluster. How do you choose between the two analyses?
    – Alek Storm
    Commented Sep 21, 2011 at 7:01
  • Well, i'm not sure that you could argue that - in both English and German /b/ and /p/ are very clearly separate phonemes and each occur in a range of environments, while in Korean the [b] is considered an allophone because it only occurs in a very restricted environment. By 'specific phonetic environment' I meant 'restricted phonetic environment', as noted by @JoFrhwld above. It would be difficult to argue for [b] as the underlying phoneme in Korean because /p/ is clearly much more versatile. Commented Sep 22, 2011 at 22:39
  • So the underlying phoneme can be determined by counting the phonetic environments that each allophone appears in, and choosing the one with the greatest? How many segments to the left and right do we include in the "phonetic environment"?
    – Alek Storm
    Commented Sep 23, 2011 at 1:25
  • No, never just counting phonetic environments - you would also need to show that the phone that occurs in more restricted contexts is likely to be affected by these contexts. The justification for phone/allophone will be language-specific, informed by the language's phonological processes, phonotactics and types of segments, and will also draw on relevant phonological and phonetic theory. There is no one-size fits all answer. But it would never make sense to say that the phoneme is the phone that is a) least frequent b) most restricted c) plausibly affected by its surrounding environment. Commented Sep 24, 2011 at 7:17
  • Each of those factors are weighted differently by different theoreticians. For example, choosing the analysis that yields the most parsimonious account of phonotactics often forces us to concede a new phoneme in the language's inventory. Whether this approach is taken depends on the personal taste of whoever is conducting the analysis. This tells us nothing about the human brain.
    – Alek Storm
    Commented Sep 25, 2011 at 19:39

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