Pronunciation of the morpheme “-s”

The morpheme “-s” is a sound (/s/, /z/ or /ɪz/) that is added at the end of some words. There are three different morphemes that add “s”: plural, third person singular of verbs and genitive. The three morphemes share pronunciation rules, and plural and third person share spelling rules.

The plural morpheme
Examples:
 * Written as “s” and pronounced as /s/: groups, lots, proofs, weeks
 * Written as “s” and pronounced as /z/: dogs, friends, jobs, shoes
 * Written as “s” and pronounced as /ɪz/: horses, judges, prizes
 * Written as “es” and pronounced as /z/:, companies, potatoes, tornadoes
 * Written as “es” and pronounced as /ɪz/: churches, classes, wishes

The third person singular morpheme
Examples:
 * Written as “s” and pronounced as /s/: gets, laughs, helps, thinks
 * Written as “s” and pronounced as /z/: brings, plays, seems, tells
 * Written as “s” and pronounced as /ɪz/: changes, increases, closes
 * Written as “es” and pronounced as /z/: studies, tries, vetoes
 * Written as “es” and pronounced as /ɪz/: focuses, pushes, reaches

The genitive morpheme
Examples:


 * Written as “’s” and pronounced as /s/: cat’s, Elizabeth’s, Joseph’s, Mike’s
 * Written as “’s” and pronounced as /z/: Barbara’s, dog’s, John’s, Mary’s
 * Written as “’s” and pronounced as /ɪz/: Boris’s, Marge’s, Rose’s, virus’s
 * Written as “’” and not pronounced (plurals): cats’, dogs’
 * Written as “’” and not pronounced (classical and biblical names): Augustus’, Jesus’, Moses’

See also: Possessive apostrophe

Classification of sounds
For the “-s” morpheme, sounds must be classified in voiced, unvoiced and sibilant

Sibilants
Sibilants are consonants that have a hissing sound.

English sibilants are /s/, /z/, /tʃ/, /dʒ/, /ʃ/ and /ʒ/.

Pronunciation of the morpheme “-s”
The ending sound of the base word determines the pronunciation of the morpheme “-s”.
 * /s/ for non-sibilant voiceless consonants /f/, /k/, /p/, /t/, and /θ/.
 * laughs, Mike’s, helps, gets, Elizabeth’s


 * /z/ for vowels and non-sibilant voiced consonants /b/, /d/, /ð/, /g/, /l/, /m/, /n/, /ŋ/, /r/, and /v/.
 * areas, Barbara’s, companies, employees, laws, plays, shoes, shows, vetoes
 * jobs, friends, breathes, dogs, tells, seems, Ann’s, brings, Oscar’s, loves


 * /ɪz/ for sibilants: /s/, /z/, /tʃ/, /dʒ/, /ʃ/ and /ʒ/.
 * buses, advises, churches, Marge’s, pushes, garages