If you have a sound change or allophony rule such as:

X -> Y / _Z

Is there a common term for X and Y?

  • 4
    Oddly, not really a term that’s often needed, for diachronic sound changes at least. I don’t think I’ve ever needed a term for this, but I guess I would probably use the same terms as for any other rule that acts on something and changes it: input and output forms. Jul 2, 2023 at 8:52
  • There might be some info here, section 2 discusses phonological rules, I believe referring to _Z as the “phonological environment” arxiv.org/pdf/cs/0204025v1.pdf
    – Julius H.
    Jul 8, 2023 at 19:01

2 Answers 2


Y is often called a reflex, though that term is used not just for sounds but also for morphemes or words: e.g. you can say that the French reflex of Latin /k/ before /a/ is /ʃ/, or that the French reflex of Latin caper is chèvre. Proto-phoneme is sometimes used for X, but this is less common (probably because there's less often a practical need for such a term).

  • 2
    This is true when describing historical changes, but not synchronic ones. For example, in the synchronic English rule R → R̥ / _P[-voice] (= resonants become voiceless after voiceless stops, so the /l/ in place is actually [l̥]), you wouldn’t call [l̥] the reflex of a proto-phoneme /l/. In a looser sense, reflex can also be used for outcomes of other processes than just sound change; e.g., you can say that अहं ahám is the Sanskrit reflex of PIE *ég̑ō (or however exactly you prefer to reconstruct it), even though the -m is analogical. Jul 7, 2023 at 7:39
  • @JanusBahsJacquet Right -- I assumed the OP was asking about diachronic sound changes. (I wouldn't describe an allophony rule as a "synchronic sound change", but maybe others do.)
    – TKR
    Jul 7, 2023 at 17:22

For a synchronic rule, this can be called an underlying form/representation being realized into a surface form/representation.

  • 1
    Assuming that the rule being described is the only one affected the sound in question. If there are multiple rules, the input of the rule may not be the underlying form, and the output may not be the surface form – both can be intermediate forms between the underlying and surface forms. Jul 11, 2023 at 17:08

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