The audio here is generated speech. A recorded human voice for this lesson is on the way.
The two sounds
S and Z are made with the tip of your tongue close to the ridge behind your top teeth, letting air hiss through a narrow gap. S is voiceless, like a snake. Z is the same with your voice on, like a bee. Put your hand on your throat and say "sss", then "zzz". The buzz is only on Z.
The letter S often makes a Z sound, which is why this matters so much. Plurals and verb endings after a voiced sound are Z: "dogs", "bags", "plays", "goes". After a voiceless sound they are S: "cats", "books", "walks". "Is", "was" and "has" all end in Z.
Hear the difference
Tap each word. Then test your ear.
The S in plural "dogs" and "plays" is a Z sound. In "cats" and "books" it stays S.
Say it out loud
Tap a sentence to hear it. Say it after the voice.
"Close" (shut) ends in Z. "Close" (near) ends in S.
Practice · 3 min
Repeat each sentence. Put a hand on your throat and feel the buzz on every Z sound, including the S in "goes", "his", "dogs" and "peas". Then record the last sentence and check that "lose" and "loosen" sound different.
Say it today
Use it once in a real conversation before tomorrow. Out loud counts, even to yourself.