Phonemes that are contrastive in certain environments may not be contrastive in all environments. In the environments where they do not contrast, the contrast is said to be
neutralized. In these positions it may become less clear which phoneme a given phone represents.
Absolute neutralization is a phenomenon in which a segment of the
underlying representation is not realized in any of its
phonetic representations (surface forms). The term was introduced by
Paul Kiparsky (1968), and contrasts with
contextual neutralization where some phonemes are not contrastive in certain environments. Some phonologists prefer not to specify a unique phoneme in such cases, since to do so would mean providing redundant or even arbitrary information – instead they use the technique of
underspecification. An
archiphoneme is an object sometimes used to represent an underspecified phoneme. An example of neutralization is provided by the Russian vowels and . These phonemes are contrasting in
stressed syllables, but in unstressed syllables the contrast is lost, since both are
reduced to the same sound, usually (for details, see
vowel reduction in Russian). In order to assign such an instance of to one of the phonemes and , it is necessary to consider
morphological factors (such as which of the vowels occurs in other forms of the words, or which
inflectional pattern is followed). In some cases even this may not provide an unambiguous answer. A description using the approach of underspecification would not attempt to assign to a specific phoneme in some or all of these cases, although it might be assigned to an archiphoneme, written something like , which reflects the two neutralized phonemes in this position, or {{IPA|{a|o}}}, reflecting its unmerged values. A somewhat different example is found in English, with the three
nasal phonemes . In word-final position these all contrast, as shown by the minimal triplet
sum ,
sun ,
sung . However, before a
stop such as (provided there is no
morpheme boundary between them), only one of the nasals is possible in any given position: before , before or , and before , as in
limp, lint, link (, , ). The nasals are therefore not contrastive in these environments, and according to some theorists this makes it inappropriate to assign the nasal phones heard here to any one of the phonemes (even though, in this case, the phonetic evidence is unambiguous). Instead they may analyze these phonemes as belonging to a single archiphoneme, written something like , and state the
underlying representations of
limp, lint, link to be , , . This latter type of analysis is often associated with
Nikolai Trubetzkoy of the
Prague school. Archiphonemes are often notated with a capital letter within double virgules or pipes, as with the examples and given above. Other ways the second of these has been notated include , {{IPA|{m, n, ŋ}}} and . Another example from English, but this time involving complete phonetic convergence as in the Russian example, is the flapping of and in some American English (described above under
Biuniqueness). Here the words
betting and
bedding might both be pronounced . Under the
generative grammar theory of linguistics, if a speaker applies such flapping consistently, morphological evidence (the pronunciation of the related forms
bet and
bed, for example) would reveal which phoneme the flap represents, once it is known which morpheme is being used. However, other theorists would prefer not to make such a determination, and simply assign the flap in both cases to a single archiphoneme, written (for example) . Further mergers in English are
plosives after , where conflate with , as suggested by the alternative spellings
sketti and
sghetti. That is, there is no particular reason to transcribe
spin as rather than as , other than its historical development, and it might be less ambiguously transcribed . ==Morphophonemes==