How to Pronounce Plural -S Endings: /s/, /z/ and /ɪz/

The final -s has three pronunciations: /s/, /z/ and /ɪz/. Which one you use depends on the last sound of the word it attaches to, not on the spelling. Cats is /kæts/, dogs is /dɒɡz/, and buses is /ˈbʌsɪz/.

Only /ɪz/ adds a syllable. The other two attach to the word without changing its length. Type any plural into the pronunciation Studio to hear which of the three it takes.

The rule in one table

Check the six sounds in the first row before anything else, because they override the voicing test. After that, decide whether the final sound is voiced or voiceless.

The voiceless sounds that take /s/ are /p/, /t/, /k/, /f/ and /θ/. That is the complete list, and it is short. Everything else in English is voiced, including every vowel, which is why /z/ is by far the most common of the three.

Why the six sounds are special

The six that trigger /ɪz/ are called sibilants, and they have something in common: they all involve a hiss or a buzz made near the ridge behind your teeth. /s/ and /z/ are the obvious ones, /ʃ/ and /ʒ/ are the sh in shoe and the middle of measure, and /tʃ/ and /dʒ/ are the ch in church and the j in jam.

Try saying bus and then adding a plain /s/. You get a slightly longer s, and nothing a listener could identify as a plural. The ending is invisible because it is too similar to the sound in front of it.

English solves this by inserting a vowel to hold the two apart, which is why buses has two syllables. It is the same fix the language applies to -ed after /t/ and /d/, covered in the -ED pronunciation guide.

The other two groups are solving a different problem. Voicing takes time to switch on and off, so the ending simply continues whatever the previous sound was doing. After voiceless /k/ in books, the voice is already off, so the ending is /s/. After voiced /ɡ/ in dogs, the voice is already on, so it is /z/. If the voiced and voiceless distinction is new, the throat test there takes a second to learn.

Group 1: -s said as /ɪz/

Only after the six sibilants. These are the plurals that gain a syllable.

Boxes is worth a look. The word ends in the letter x, which spells two sounds, /ks/. The final one is /s/, a sibilant, so the plural takes /ɪz/.

Some speakers and dictionaries write this ending /əz/ rather than /ɪz/. Both describe the same weak vowel, and this site uses /ɪz/ throughout.

Group 2: -s said as /s/

After /p/, /t/, /k/, /f/ or /θ/. No extra syllable.

Months /mʌnθs/ is the hardest of these. Three consonants in a row at the end, with no vowel to rest on, and many fluent speakers simplify it to something closer to /mʌns/ in fast speech. The consonant clusters guide covers why these endings resist.

Group 3: -s said as /z/

After any voiced sound that is not a sibilant, which means most of the language.

Notice how many of these end in vowels. Every English vowel is voiced, so every word ending in a vowel sound takes /z/, with no exceptions at all. That single fact covers a large share of English plurals.

Words that change before the ending

A small group changes its final consonant when the plural is added. These are genuine irregularities and have to be learned one at a time.

The f words announce themselves in the spelling, since the plural is written with a v. The th words do not, which makes baths and mouths worth a second look. American English commonly keeps /θs/ in baths, so both /bɑːðz/ and /bæθs/ are standard in their own varieties.

Not every f word does this. Roofs, cliffs, chiefs and beliefs keep the /f/ and take a plain /s/.

The same rule for verbs and possessives

This is not a plural rule. It is a rule about a final -s of any kind.

Third-person verbs follow it exactly: works /wɜːks/, plays /pleɪz/, watches /ˈwɒtʃɪz/, runs /rʌnz/, stops /stɒps/, misses /ˈmɪsɪz/.

Three common verbs change their vowel as well, which is a separate irregularity: does is /dʌz/ rather than /duːz/, says is /sɛz/ rather than /seɪz/, and goes is /ɡəʊz/, which is regular but often misread.

Possessives follow it too: Mark’s /mɑːks/, John’s /dʒɒnz/, the church’s /ˈtʃɜːtʃɪz/. A name already ending in a sibilant gains a syllable in the possessive just as a plural would, so James’s is /ˈdʒeɪmzɪz/.

One consequence is that cats, cat’s and cats’ are all said /kæts/. The apostrophe is a spelling device with no sound of its own, which is exactly why it is so often misplaced in writing.

Why /z/ turns up more often than /s/

Counting the two lists makes the point. Five English sounds are voiceless and take /s/. Everything else takes /z/, and “everything else” includes all twenty or so vowels plus around thirteen consonants.

The practical consequence is that if you are unsure and have to guess, /z/ is the better bet by a wide margin. It is also the direction that most learners need to move in, since the letter s on the page pulls everyone towards /s/.

There is a listening consequence too. Because the final /z/ is quiet and often shortened in running speech, plurals can be genuinely hard to catch. English speakers rely on other cues as well, such as the verb form and any numbers in the sentence, so a missed /z/ rarely causes a misunderstanding on its own. That is worth knowing when you are worried about being understood: the ending matters, but it is not carrying the sentence alone.

What happens to -s in a real sentence

The ending behaves like any other final consonant once words start running together.

A final /s/ or /z/ links straight onto a following vowel, so books are sounds like boo-ksar, and cars arrive sounds like car-zarrive. There is no pause at the word boundary.

Before another /s/ or /z/, the two merge into a single slightly longer sound. Books shop and his sister both produce one continuous hiss rather than two separate ones, and nobody hears a missing word.

The ending also picks up voicing from what follows in fast speech. Dogs bark keeps its /z/, because /b/ is voiced. Dogs come can shade towards /s/, because /k/ is not. That is ordinary assimilation, and it is covered more fully in the connected speech guide.

The /ɪz/ ending, once again, never reduces. A syllable is a syllable.

The mistakes people actually make

Using /s/ everywhere. Saying dogs as /dɒɡs/ rather than /dɒɡz/. This comes from reading the letter rather than hearing the sound, and it is the most common error by a wide margin.

Adding a syllable where none belongs. Saying cats as CAT-us. The ending only becomes a syllable after the six sibilants.

Dropping the syllable where it does belong. Saying watches as watch. Here the syllable carries the entire plural, so losing it loses the grammar.

Dropping the ending altogether. Many languages do not allow a consonant cluster at the end of a word, so friends /frɛndz/ can come out as friend. This is a cluster difficulty rather than a rule problem, and it responds to cluster practice rather than to more rule study.

Practice

Say each word, then decide which ending it takes. Cover the answers first.

1. books
2. roses
3. cars
4. months
5. bridges
6. leaves
7. cups
8. songs
9. beaches
10. days
11. hands
12. laughs
13. houses
14. plants
15. keys

Numbers 12 and 13 are the two worth rechecking. Laughs ends in /f/ despite the spelling, and houses changes a sound that nothing in the writing warns you about.

Second practice: sentences

Single words are the easy case. Read each sentence aloud at normal speed and check every -s in it.

1. She watches films and reads books.
2. The boxes are on the shelves.
3. My friend’s houses both have gardens.
4. He laughs at all my jokes.
5. Three months of classes finishes in May.

Sentence 5 is the useful one. Two /ɪz/ endings and one /s/ in a single short line is exactly where people start applying one ending to everything in sight.

A five-second check for any word

1. Say the word out loud and stop at the last sound. Ignore the letters.
2. Is it one of /s/, /z/, /ʃ/, /ʒ/, /tʃ/ or /dʒ/? If yes, the ending is /ɪz/ and the word gains a syllable. Stop here.
3. If not, hold that final sound with your fingers on your throat.
4. Buzzing means the ending is /z/. Silence means the ending is /s/.
5. Either way, no syllable is added.

Step one is the one that gets skipped, and it is the one that matters. The whole rule runs on sound, and the spelling is what leads people to the wrong answer.

To check any individual word, type it into the Studio and read the transcription. The -ED ending works on the same principle, so the -ED guide is worth reading alongside this one: learn them together and you have covered the two most frequent endings in English.