Fortis / Lenis
In Zapotec languages, fortis typically corresponds to voicelessness and extra length in obstruents and extra length in sonorants. Lenis corresponds to voicing and less length in obstruents and less length in sonorants. In addition, stressed vowels before lenis consonants may be longer than those before fortis consonants.
Read more about this topic: List Of Zapotec Languages, Phonetics and Phonology