Background: The principles of phonological analysis can be applied independently of modality because they are designed to serve as general analytical tools, not language-specific ones. The same principles have been applied to the analysis of sign languages (see Phonemes in sign languages), even though the sub-lexical units are not instantiated as speech sounds.
Question: What other types of language have the phonological analysis principles been applied to?
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<extra_id_0> sign languages<extra_id_1>