Laurie Bauer - WordPress.com — Get a Free Blog Here

THE LINGUISTICS STUDENT’S HANDBOOK 36
The underscore, often termed the environment bar, shows the position in
which the affected element has to be for the change described by the rule to take
place. Consider the examples in (4), where, as is customary, C indicates ‘any
consonant’, V indicates ‘any vowel’ and # indicates a boundary (the precise
nature of the boundary need not concern us in detail just yet).
(4) a. d → ð / V ___ V
b. r → Ø / ___ C
#
� �
� �
c. [� voice] → [�voice] / �obstruent
___
#
(4a) is a rule with the full environment specified. It states that [d] (presumably
a dental [d], though this is not stated explicitly in the rule and must be
deduced from what else we know about the language in which this rule applies)
becomes a fricative when it is immediately preceded by a vowel and immediately
followed by a vowel. In other words, sequences of [ado], [ida] will be
affected by the rule, and the stop will be replaced by a fricative, while sequences
of [nda], [#da], [adr], [ad#] will not be affected, and the plosive articulation
will be retained. This rule could be seen as a first approximation to a rule of
allophony in Spanish. Note that when we use phonetic symbols in rules of this
kind we do not enclose them in phonemic slashes or phonetic brackets. This is
partly to prevent the rule statement from becoming too cluttered, but it is also
theoretically motivated in that we may not wish to take a stance on whether the
sounds involved are or are not contrastive units.
In (4b) no environment is specified to the left of the environment bar, and
this indicates that nothing in the environment in this position is relevant to the
operation of the rule. The braces to the right of the environment bar indicate
options: the rule will apply equally well if there is a C here or if there is a #boundary
in this position. Thus this rule states that [r] will be deleted from
sequences such as [ər#], [ərd], [trt], [lr#] and even [#r#], but will not be
deleted from [trə]. Of course, not all of these strings will necessarily exist in the
input. If we take it that (4b) is a first approximation to a rule for the deletion of
[r] in non-rhotic varieties of English, for example, there will never be a [trt]
input because this can never arise in the phonology of English. This does not
make (4b) a poor rule. The important thing is that (4b) should cover the data
for which it is intended to provide an account. A rule will sometimes make predictions
about data which has not been included, and if so the generality of the
rule can be tested against new data.
In (4c) the environment bar is within a particular phonological segment. The
square brackets in (4c) enclose a single phonological segment, and do not imply