14 Types of Phonological Rules
In spoken language, one important pattern is how certain phones are pronounced differently, yet are treated as the same conceptual object by speakers. For example, consider the English words atom and atomic. In most varieties of North American English, the consonant phone in the middle of atom is pronounced as an alveolar flap; remember that the alveolar flap is symbolized in the IPA by [ɾ]. But in the word atomic, the corresponding phone is a voiceless alveolar stop followed by a notable puff of air, symbolized in the IPA as [tʰ], where the superscript [ʰ] represents the puff of air (called aspiration). However, these two words are clearly related: atomic is built from the word atom, both in pronunciation and in meaning. Because of this, it is convenient to think of these two sounds as being the same object on some abstract conceptual level, despite being physically different.
This object is called a phoneme, and its various physical realities as phones are called its allophones. We can think of a phoneme as a set of allophones, with each one connected to certain specific positions. So in this case, we might say that the set {[ɾ], [tʰ]} is a phoneme, with [ɾ] and [tʰ] each being allophones of that phoneme, used in different situations, called environments.
The most common types of environments require one or more specific phonetic properties immediately to the left, one or more specific phonetic properties immediately to the right, or a combination of both. As with most aspects of linguistics, the environments for allophones can be more complex than what is presented in the simpler cases discussed in this textbook.
By convention, phonemes are often notated with just a single symbol in slashes / /, because the number of allophones can get quite large, and it would be too cumbersome to continue listing out all of the allophones as a set. The choice of symbol depends on certain assumptions, but for now, we can represent this phoneme with /t/.
Both of these allophones of /t/ occur between two vowels or syllabic consonants, but the flap [ɾ] is followed by an unstressed vowel or syllabic consonant, while the aspirated [tʰ] is followed by a stressed vowel or syllabic consonant. So we might conjecture that stress is at least partially responsible for determining which allophone to use for /t/.
We can test that conjecture by looking at other words where this phoneme occurs (fortunately, it is often spelled with the letter <t> in English) and seeing which allophone is used. In [ˈmɛɾl̩] metal and [məˈtʰælək] metallic, we see the same pattern as in atom and atomic, so our conjecture holds. There are other pairs of related words that show the same pattern: [ˈbæɾl̩] battle and [bəˈtʰæljn̩] battalion, [ˈkrɪɾək] critic and [kraɪˈtʰiriə] criteria, etc.
If we look beyond related words, we see the same pattern. English words with /t/ between two vowels or syllabic consonants tend to have the flap [ɾ] if the second is unstressed but aspirated [tʰ] if the second is stressed. That is, words like data, writer, and Ottawa have [ɾ], while words like attack, return, and Saskatoon have [tʰ]. So we can say that these two allophones are used according to a phonological rule that governs their distribution.
Every language has many phonological rules. Phonological rules alter the underlying structure and form of words and sentences. Next, we are going to classify phonological rules according to the kind of process that they involve. Seven major types of processes are discussed here, along with examples from the phonology of English or other languages.
Rules of assimilation cause a sound to become more like a neighboring sound with respect to some phonetic or articulatory property. In other words, the segment affected by the rule assimilates or takes on a property from a nearby segment. Rules of assimilation are very common in languages. An example of assimilation is the assimilation in place of articulation of nasals, for example this is easily observable in the pronunciation of the prefix un- in English. Words like unbelievable, unstable, and unclear are often pronounced [ᴧmbəlivəbl]̩ , [ᴧnsteɪbl]̩ , and [ᴧŋkliɹ]. That is, the nasal [n] is often pronounced as a bilabial nasal when it occurs before a bilabial sound, as in unbelievable, and as a velar nasal when it occurs before a velar sound, as in unclear. This is called Nasal Place Assimilation because the nasal /n/ changes its place of articulation.
Another assimilation process is palatalization. Palatalization refers to a special type of assimilation in which a consonant becomes like a neighboring palatal. For example, when American English speakers say Did you? rapidly, they very often pronounce it as [dɪʤu]. The sounds [d] (the alveolar stop from the end of did) and the palatal glide from the beginning of you combine to form the post-alveolar affricate [ʤ]. In this case, the palatal nature of the glide has been assimilated by the stop, making it a post-alveolar affricate. High and mid front vowels such as [i] and [e] also cause this change. The most common types of palatalization occur when alveolar, dental, and velar stops or fricatives appear before a front vowel. So the following are all common types of palatalization: [t] → [ʧ]; [d] → [ʤ]; [s] → [ʃ]; [k] → [ʧ]; [ɡ] → [ʤ]. While there are variants on palatalization, and other sounds can be palatalized, the main things to look for are a sound becoming a palatal or post-alveolar.
Dissimilation. Unlike assimilation, which makes sounds more similar, rules of dissimilation cause two close or adjacent sounds to become less similar with respect to some property, by means of a change in one or both sounds. An example of dissimilation in Greek is the following: A stop becomes a fricative when followed by another stop. In fast speech specially, the form /epta/ ‘seven’ can be pronounced as [efta], and /ktizma/ ‘building’ can be pronounced as [xtizma] ([x] is a voiceless velar fricative).
In the case of epta, the [p] and [t] sounds share a manner of articulation which is that they are both stop consonants, same as the sounds [k] and [t] sounds. Thus, according to this dissimilation rule, since there cannot be two stops together, the first one must become a fricative consonant.
Phonological rules of insertion cause a segment not present at the phonemic level to be added to the phonetic form of a word. An example of this kind of rule from English is voiceless stop insertion. Between a nasal consonant and a voiceless fricative, a voiceless stop with the same place of articulation as the nasal is inserted.
Thus, for instance, the voiceless stop insertion rule may apply to the words dance /dæns/ → [dænts], strength /stɹɛŋθ/ → [stɹɛŋkθ], and hamster /hæmstɹ̩/ → [hæmpstɹ̩]
Deletion rules eliminate a sound that was present at the phonemic level. Such rules apply more frequently to unstressed syllables and in casual speech. English examples include the delition of /h/ in unstressed syllables. This deletion rule would apply to a sentence such as He handed her his hat /hi hændəd hɹ̩ hɪz hæt/ to be pronounced as [hi hændəd ɹ̩ ɪz hæt]. Deletion is common in fast speech because it saves time and articulatory effort.
Metathesis. Rules of metathesis change the order of sounds. In many instances, sounds metathesize in order to make words easier to pronounce or easier to understand. In Leti, an Austronesian language, consonants and vowels switch places when a word that ends in a consonant is combined with a word that starts with two consonants. The last two sounds in the first word trade places to avoid having three consonants in a row.
Rules of strengthening (also called fortition) make sounds stronger. The rule of English aspiration, as stated below, provides an example:
Voiceless stops become aspirated when they occur at the beginning of a stressed syllable. The pronunciations of pat [phæt] and top [thɑp] illustrate the application of the English aspiration rule. Aspirated stops are considered to be stronger sounds than unaspirated stops because the duration of voicelessness is much longer in aspirated stops (since it extends through the period of aspiration).
Rules of weakening cause sounds to become weaker. The “flapping” rule of English is an example of weakening. The flap [ɾ] is considered to be a weaker sound than [t] or [d] because it is shorter and it obstructs air less. An alveolar stop is realized as [ɾ] when it occurs after a stressed vowel and before an unstressed vowel.
Adapted from:
Anderson, C., Bjorkman, B., Denis, D., Doner, J., Grant, M., Sanders, N. & Taniguchi, A. (2022). Essentials of Linguistics. Pressbooks. https://ecampusontario.pressbooks.pub/essentialsoflinguistics2/