Chapter 4: Phonology

4.9 Types of phonological rules

Phonation assimilation

There are many types of rules that languages may have. Perhaps the most common general type of phonological rule we find is assimilation, when a phoneme changes to an allophone that matches some aspect of its environment. That is, one or more of the properties in the rule’s change are also present somewhere in the rule’s environment. We see this with French devoicing, where the sonorants become voiceless in an environment that also involves voicelessness.

Phonation assimilation can also cause voicing rather than devoicing, as in Wemba Wemba (an extinct Kulinic language of the Pama–Nyungan family, formerly spoken in Australia), in which voiceless plosives are voiced after nasal stops, as in the following data (adapted from Hercus 1986).

/panpar/ [latex]\rightarrow[/latex] [panbar] ‘shovel’

/jantaŋ/ [latex]\rightarrow[/latex] [jandaŋ] ‘I’

/taɳʈa/ [latex]\rightarrow[/latex] [taɳɖa] ‘touch’

We can write the relevant rule as follows:

  • plosive [latex]\rightarrow[/latex] voiced / voiced nasal stop

In both the French and Wemba Wemba assimilation rules, the crucial part of the environment containing the assimilating property is on the left, but phonation assimilation can also depend on the right side of the environment, as in Polish (a West Slavic language of the Indo-European family, spoken in Poland). In Polish, voiced obstruents become voiceless if followed by a voiceless obstruent (data adapted from Stanisławski 1978 and Rubach 1996).

/dxu/ [latex]\rightarrow[/latex] [txu] ‘of breath’

/rɪbka/ [latex]\rightarrow[/latex] [rɪpka] ‘little fish’

/vçi/ [latex]\rightarrow[/latex] [fçi] ‘of village’

/vɪkaz pism/ → [vɪkas pism] ‘list of journals’

The relevant phonological rule can be written as follows:

  • obstruent [latex]\rightarrow[/latex] voiceless / voiceless obstruent

Place assimilation

Phonation is not the only phonetic property that can assimilate. In Persian (a Southwestern Iranian language of the Indo-European family, spoken in Iran and surrounding areas), we see assimilation of place, with alveolar stops becoming postalveolar before a postalveolar (data adapted from Bijankhan 2018).

/ʔætʃɒn/ [latex]\rightarrow[/latex] [ʔæṯʃɒn] ‘parched’

/χædʃe/ [latex]\rightarrow[/latex] [χæḏʃe] ‘flaw’

/ʔenʃɒ/ [latex]\rightarrow[/latex] [ʔeṉʃɒ] ‘essay’

The relevant phonological rule can be written as follows:

  • alveolar stop [latex]\rightarrow[/latex] postalveolar / postalveolar

Nasality assimilation

Nasality is also another common property that assimilates, as in Ka’apor (a.k.a. Urubú-Kaapor, a Wayampí language of the Tupian family, spoken in Brazil). In Ka’apor, vowels are nasalized after a nasal stop (data adapted from Kakumasu 1986).

/uruma/ [latex]\rightarrow[/latex] [urumã] ‘duck’

/tamui/ [latex]\rightarrow[/latex] [tamũi] ‘old man’

/mɨra/ [latex]\rightarrow[/latex] [mɨ̃ra] ‘wood’

/nino/ [latex]\rightarrow[/latex] [nĩnõ] ‘lie down’

/niʃoi/ [latex]\rightarrow[/latex] [nĩʃoi] ‘none’

/ne/ [latex]\rightarrow[/latex] [nẽ] ‘you (sing.)’

The relevant phonological rule can be written as follows:

  • V [latex]\rightarrow[/latex] nasal / nasal stop

Other kinds of rules

Most any phonetic property can assimilate, and there are also many rules that do not involve assimilation at all.

[more examples coming soon!

Using common rules types

Knowing what kinds of phonological rules we are likely to find helps narrow down our options when trying to determine what phones are allophones of the same or different phonemes. For example, for the French sonorants, we see that there are natural pairs of voiced and voiceless sonorants, so it would be reasonable to see if the distribution of these match what we know about rules that affect voicing, such as assimilation.

By taking advantage of our knowledge of common types of rules, this allows us to avoid focusing on likely irrelevant factors. For example, for French, we would know not to worry too much about vowel rounding or place of articulation, since these are not normally triggers for changing phonation. We can also begin looking for patterns based on common rules without even knowing which phones of interest we should examine: maybe there is a pattern in vowel nasality based on the presence or absence of an adjacent nasal stop (indicating assimilation of nasality). Of course, the language we are analyzing won’t have all of these rules, but it might have one, so we can get a head start on analyzing its phonology.

This means that phonemic analysis and rule discovery go hand in hand. Sometimes, we may use known phonological rules to help uncover distributional patterns in phones, and other times, we may find the distributional patterns first, leading us to posit a phonological rule. Working on a language from both directions can be much more productive than trying to do phonemic analysis directly. This is a method that permeates all of linguistics, not just phonology. Every language we analyze tells us something about how language itself works, and that broader knowledge of how language works helps us to analyze the next language.

Check your understanding

Coming soon!


Bijankhan, Mahmood. 2018. Phonology. In The Oxford handbook of Persian linguistics, ed. Anousha Sedighi and Pouneh Shabani-Jadidi, Oxford Handbooks in Linguistics, 111–141. Oxford: Oxford University Press.

Hercus, Luise A. 1986. Victorian languages: A late survey. No 77 in Pacific Linguistics Series B. Canberra: The Australian National University.

Kakumasu, James. 1986. Urubu-kaapor. In Handbook of Amazonian languages, ed. Desmond C. Derbyshire and Geoffrey K. Pullum, vol. 1, 326–404. Berlin: Mouton de Gruyter.

Rubach, Jerzy. 1996. Nonsyllabic analysis of voice assimilation in Polish. Linguistic Inquiry 21(1): 69–110.

Stanisławski, Jan. 1978. Wielki słownik polsko-angielski. Warsaw: Wiedza Powszechna.


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Essentials of Linguistics, 2nd edition by Catherine Anderson; Bronwyn Bjorkman; Derek Denis; Julianne Doner; Margaret Grant; Nathan Sanders; and Ai Taniguchi is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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