In theoretical linguistics
is a phenomenon where certain features
are omitted in underlying representations
. Restricted underspecification theory holds that features should only be underspecified if their values are predictable. For example, in English
, all front vowels
. It is not necessary for these phonemes
to include the distinctive feature
[−round], because all [−back] vowels are [-round] vowels, so the distinctive feature is not distinctive if we know the vowel to be front. Radical Underspecification theory, on the other hand, also allows for traditionally binary features to be specified for only one value, where it is assumed that every segment not specified for that value has the other value. For example, instead of the features [+voice] and [−voice], only [+voice] is specified and voicelessness is taken as the default.