Two or more segments are tautosyllabic (with each other) if they occur in the same syllable. For instance, the English word "cat",, is monosyllabic and so its three phonemes pronounced as //k//, pronounced as //æ// and pronounced as //t// are tautosyllabic. They can also be described as sharing a 'tautosyllabic distribution'.
Phonemes that are not tautosyllabic are heterosyllabic. For example, in the English word "mustard", pronounced as //m// and pronounced as //t// are heterosyllabic since they are members of different syllables.
. Language History. Andrew Sihler. John Benjamins Publishing. Amsterdam/Philadelphia. Current Issues in Linguistic Theory. 191. 2000. 277. 90-272-3698-4.