The Big Idea
I get asked this question a lot, “How do you know when the “s” at the end of a word is pronounced as an /s/ or a /z/?”
I also help a lot of people stop adding extra syllables to past tense verbs when they shouldn’t be there.
The information I reorganized from my teaching material includes a lot of tables with examples that are difficult to show on Substack. I’m going to type the big ideas and rules here and link to the document so you can download it and use it as a reference.
I created a practice spreadsheet where you have to choose what the final sound will be for the “-ed” and “-s” endings. It’s a Google sheet so you can download it and save it.
English can look very different than it sounds.
The sound at the end of the base word determines how the suffix is pronounced.
Past tense “-ed” can sound like /t/, /d/, or /əd/.
Plural/possessive/3rd-person “-s” can sound like /s/, /z/, or /əz/.
Rules help answer questions about what is happening and why. Noticing the patterns of when it’s happening will make this easier to sustain in your speech for the long term.
Use these three rules to practice.
Start noticing these patterns.
When your voice is off, leave it off.
→ voiceless endings make voiceless suffixes (/t/ or /s/)
When your voice is on, leave it on.
→ voiced endings make voiced suffixes (/d/ or /z/)
Made in the same place, make some space.
→ If a word ends in the same place (tongue position) as the suffix, add an extra syllable. Schwa /əd/ or short-i /ɪd/ are both acceptable.
“-ed” after /t/ or /d/ = /əd/
-s after /s, z, ʃ, ʒ, tʃ, dʒ/ = /əz/
I also call this my “cats” and “dogs” rule for the “-s” endings:
When your voice is off, leave it off.
→ “cat” (ends in voiceless /t/) + s = “cats” = looks like an “s” and sounds like an “s”
When your voice is on, leave it on.
→ “dog” (ends in voiced /g/) + s = “dogs” - looks like an “s” but sounds like a “z”
Final Stop Consonant Sounds - When They’re Silent
The stop consonants are: /p, b, t, d, g, k/
When a word ends with a stop consonant sound, the air won’t be released so you won’t hear the final sound unless there’s a word following it that begins with a vowel.
If “work” is at the end of a sentence, before a pause, or before a word that begins with a consonant, the tongue (or lips) goes to that position but just holds in the airflow.
“I have to go to work.” - You won’t hear a /k/ sound because it’s at the end of a sentence.
vs
“I have to work on my car.” - You will hear the /k/ sound because the airflow is released as you start making the vowel after it, “on.”
vs
“I have work to do.” - You won’t hear a /k/ sound because it’s followed by a consonant /t/.
Keep that in mind when reading the following examples aloud.
Read-Aloud Practice (Short Sentences)
• I locked our lab and walked out.
• She stayed up late and filed all the reports.
• They waited outside and chatted.
• The dog plays all day with others.
• He verifies our data; she matches our records.
• We boxed up the samples and shipped everything.
• The code compiled and deployed as expected.
• This process stabilizes results during tests.
I created a practice spreadsheet where you have to choose what the final sound will be for the “-ed” and “-s” endings. It’s a Google sheet so you can download it and save it.