Students understanding the complexity of language

Chapter 11.10: Phonological Features


chapter 11.10: features and rules

As discussed in the sections above on consonants and vowels, phonemes can be categorized by certain distinctive features. Understanding these features will be very important when it comes time to see how sounds can change into other sounds.

Features are given in a binary form between square brackets, using the plus (+) or minus (-) signs to indicate whether a particular phoneme has or does not have that feature. For example, we learned that the phoneme /p/ was a bilabial voiceless stop. Because it is a labial consonant, we can use the notation [+labial], whereas a consonant like /t/ would be [-labial]. Because it is voiceless, we can use the notation [-voice], whereas a sound like /b/ is [+voice]. Because it is a stop, in which the air flow through the oral cavity is completely obstructed, it can be notated by the feature [-continuant], where a sound like /f/ or /l/ or /e/ would all be [+continuant].

The advantage of this type of binary notation is that it makes the specific processes of various sound changes more transparent. As an example, let us continue with the sound /p/, a labial, voiceless, stop. It was mentioned earlier that the sound /p/ in Proto-Indo-European became /f/ in Germanic languages like English. This change explains why we have Latin words like piscis, pedem and pater, all beginning with /p/, while their English counterparts, fish, foot, and father, all begin with /f/. It is one thing to say that /p/ becomes /f/, but it is another thing to explain how this process takes place. How can one sound simply become another?

As already described, using feature notation we can write /p/ as

[+labial] [-voice] [-continuant]

If we look at the features for the sound [f] we have


The only difference between the two sounds is in the [continuant] feature. In other words, we are not dealing so much with one sound becoming an entirely different sound, but with a sound altering a single feature. We can write the change thus:

[+labial][-voice][-continuant] → [+labial][-voice][+continuant]

In fact, the change from [p] to [f] is part of a larger shift, called Grimm’s Law, in which all three voiceless stops, [p], [t], and [k], became voiceless fricatives [f], [θ], [h]. Because this is a universal change for all stops, we can omit the place of articulation feature and write the change thus:

[-voice][-continuant] → [-voice][+continuant]

This change covers all voiceless, non-continuants, that is, all voiceless stops, and says that they all become voiceless continuants. In other words, it says that [p], [t], [k] become [f], [θ], [h].

A simpler example of the use of features to describe changes can be seen if the following instance of assimilation. We have already learned how nasals are easily assimilated to following consonants. Take the phrase “on call.” In everyday speech, the alveolar nasal [n] in “on” is assimilated to the velar stop [k] that begins the word “call,” and becomes pronounced [ŋ]. Using feature notation we can write the change [n] > [ŋ] as

[+nasal][+alveolar] → [+nasal][+velar]

List of Distinctive Features

The following features are some (from a larger list) that we will occasionally see in this course as we discuss phonological changes. You will notice that most of them are terms you have already seen in the description of phonemes from Week 2.

  • [+/- consonant] Segments with this feature include all consonants, whether stops, fricatives, affricates, nasals, or liquids. Vowels and semivowels lack this feature.
  • [+/- continuant] This feature describes consonantal segments in which the airflow is allowed to pass through the oral cavity without stopping. It includes fricatives and liquids, but not stops or affricates.
  • [+/- approximant] As learned already, approximants are segments in which there is little to no obstruction of the air. This class includes vowels, semivowels, liquids. Segments without this feature are stops, fricatives, affricates, and nasals.
  • [+/- sonorant] Sonorant segments include vowels, semivowels, liquids and nasals. Segments without this feature are stops, fricatives and affricates.

In addition to these, there are place features such as [+labial] or [-velar] and voicing [+/- voice].

For vowels, the features [+/-high][+/-mid][+/-low], [+/-front][+/-central][+/-back], [+/-tense] and [+/-rounded] can be used.

Phonological rules

The change in Grimm’s Law wherein [p] > [f] is an unconditioned change. It happened throughout all occurrences of Indo-European [p]. But the change from [n] to [ŋ] is a conditioned change. It only occurs in certain phonetic environments, specifically, when the alveolar nasal comes before a velar sound. When we use features to describe the change like we did above, we can incorporate notation which specifies the type of phonetic environment that is necessary to cause the change.

The change we want to describe says that an alveolar nasal becomes a dental nasal whenever the alveolar nasal comes before a velar stop. So we write a phonological “rule” that describes this:

[+nasal][+alveolar] → [+nasal][+velar] /____ [+velar]

Let’s break down this equation. The first part, [+nasal][+alveolar], describes the features of the phoneme before the sound change. The arrow, → (or you can use >) represents the process of change itself, and is followed by the features after the change has occurred, in this case [+nasal][+velar]. This change is followed by a slash / that means “in the following condition,” and is followed by a description of the phonetic environment that must exist for the change to occur. In this case we have ____ [+velar]. The underscore here represents the phoneme that is being affected by the sound change. So we can read this equation as whenever a nasal alveolar phoneme occurs directly before a velar phoneme, then it will change to a nasal velar phoneme.

In effect, this rule is the same as simply saying [n] > [ŋ] before velars. By using the notation of features, we can see the underlying mechanisms that cause the change.

As second example, let’s take the “rule” that describes plurals in English. With a word like “dog,” we add the [z] to the end, so that we have [dɔgz] (or [dɑgz]). But if we add a plural to a word like “hat” we have [hæts]. One of these words has [z] and the other has [s]. The difference is that “dog” ends in a voiced sound while “hat” ends in a voiceless sound. The plural is normally voiced but becomes voiceless by assimilation when it follows a voiceless sound. We can represent this change in the following way:

[+alveolar][+continuant][+voice] → [+alveolar][+continuant][-voice] /[-voice] _____

The environment is given as /[-voice] _____, meaning that the change occurs when the sound [+alveolar] [+continuant][+voice] occurs directly after a voiceless sound. The change shows that the voiced alveolar continuant, that is, [z], becomes a voiceless, alveolar continuant, that is, [s].

In this course we will most often use the simple method for ease, but I will assume that you know the features of the sounds that we are talking about, and in some instances it will be useful to discuss the changes through the distinctive features.