When you see the letter “S” how do you know if you should pronounce it with an S-sound or a Z-sound? Knowing how to pronounce “S” can be tricky. The bad news is that there are no clear-cut rules, so you really need to learn to use your ear.

Pronouncing the sounds of S and Z

Some students have trouble hearing the difference and pronouncing the two sounds correctly. Both “S” and “Z” are made in the same place in the mouth, but the factor that distinguishes them is: voicing. For “S” the voice is off, so there is only the sound of air coming from the mouth: /s/. For “Z” there is also the sound of air, but the voice is on, so the vocal cords need to be making sound: /z/.

Pronouncing words spelled with S

Now, even if you have no trouble hearing and saying these two sounds, the spelling can leave you totally confused. English spelling does not always indicate which sound you should use.

Frequent Words

The first step is to make sure that you are pronouncing the everyday words correctly. Here are the words from the 1,000 most frequently used words of English in which the [s] is pronounced as /z/. You should definitely make sure that you are saying these words right:

is, was, as, his, these, has, isn’t, does, doesn’t, because, those, wasn’t, easy, whose, thousand, lose, cause, reason, present, raise, phrase, surprise, design, rise, choose, visit, observe, nose, rose, confuse.

However, not every word with an “S” has a Z-sound. In these words the sound is /s/:

this, its, also, us, answer, listen, pass, person, course, less, base, yes, beside, case, let’s, possible, else, itself, thus, sense, necessary, various.

What can make it seem even more confusing, is that there are sometimes differences in American and British English spellings, such as: realize/realise. These small variations in spelling do not confuse native speakers of English because they already know how the words should sound. You just need to be aware that even though the spelling looks different, the pronunciation is the same, so don’t let it confuse you.

Pronouncing Words with [-s] endings

The S and Z-sounds are also important in words that end with [-s]. The good news is, there is a clear pattern for this. The sound of an “S” at the end of a word needs to match the voicing of the sound just before it. Here are some examples to illustrate:

take — the last sound in this word /k/ is voiceless. So when an “S” is added, it matches the voicing of the “K” and is pronounced as /s/: takes

live — the last sound in this word /v/ is voiced. So when an “S” is added, it follows the voicing of the “V” and is pronounced as /z/: lives

pass — the last sound in this word is already /s/, so when “S” is added, a small vowel sound is used to separate them. And since all vowel sounds are voiced, the [-s] ending is pronounced as /z/: passes. 

So remember, keep your ears open and listen carefully so that you are not confused about pronouncing “S” and “Z”.