997: Pronunciation of -(E)S Sep 1, 2017

The majority of English nouns are pluralized with the letter '-(e)s', but this is pronounced three different ways: /s/ as with 'cats', /z/ as with 'dogs', or /ɪz/ (or /əz/ depending on one's accent) as with 'beaches'. This is not random but is based off of the sound that comes before it. In general, if a consonant precedes it and is unvoiced like /p/, /t/, or /k/ the suffix will be /s/ but if it is preceded by a voiced consonant like /b/, /d/, or /g/, or a vowel it will become /z/. There is a chart below showing voiced and unvoiced consonants, you can also feel the difference if you make the unvoiced /p/ sound and then /b/ that uses more air. There are certain sounds that act as an exception to that rule, including /s/, /z/, /tʃ/ (‘like church’), /ʃ/ (like ‘rush’), /ʒ/ (like in luge), and /dʒ/ (like in 'hedge'), because when the pluralizing suffix '-(e)s' follows those it becomes /ɪz/.

The chart is from http://gawron.sdsu.edu/intro/course_core/lectures/SSAE.html