Collection

TH vs Z Hearing TH (then) and Z apart

7 word pairs · 3 levelsUpdated October 26, 2026

TH vs Z7/20

Which word did you hear?

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Listen for

TH in 'then' is a soft buzz. Z is a sharper, stronger buzz.

How trainable is it?

The TH of then can be slow to train. In a small study by Iino and Wistner (2022), five Japanese students practiced English fricatives with an online high variability program once a week for eight weeks, and they identified this TH about 60% of the time at both the start and the end. High variability phonetic training (HVPT) does work for many sounds, as Ron Thomson's 2018 review of 32 studies found, but give this one more time than the others.

Studies: Thomson 2018 · Iino & Wistner 2022

Test your ear18 words across L vs R, B vs V and TH vs S, in about 2 minutes. See which sounds you already hear apart.Take the listening test →

Lv 1

Easy

1 pairs

Short, common words. For consonants, the sound is at the start of the word.

then · zen
Where the sound is: Start of the word

Lv 2

Medium

5 pairs

Clusters, word endings or less common words.

breathe · breeze
Where the sound is: End of the word
bathe · bays
Where the sound is: End of the word
teethe · tease
Where the sound is: End of the word
seethe · seize
Where the sound is: End of the word
writhe · rise
Where the sound is: End of the word

Lv 3

Hard

1 pairs

Middle of the word and longer words.

clothing · closing
Where the sound is: Middle of the word
Note: closing = /ˈkloʊzɪŋ/

How to hear the difference between TH and Z

Listen for the hiss inside the buzz. The TH in then is a soft, weak buzz, with air spreading out over a flat tongue. Z is a strong buzz with a sharp hiss riding on it. The skill is hearing that difference in every voice.

How TH and Z are made

For the TH in then, the tip of the tongue rests lightly against the back of the upper teeth, or just between the teeth, and the voice buzzes while air slips out over the flat tongue. The sound is soft and quiet.

For Z, the tongue tip moves back to the ridge behind the teeth and forms a narrow groove. Air rushes through it against the teeth, the same sharp hiss as S, with the voice buzzing underneath.

The TH in then is the voiced partner of the TH in think, the way Z is the voiced partner of S.

Why do TH and Z sound the same to Japanese speakers?

Japanese has no TH, so the ear files the TH of then under the closest sound it has, the z of ザ行 (the za row). Katakana writes the two the same way: then and zen are both ゼン (zen), and breathe and breeze are both ブリーズ (buriizu).

At the start of a word, Japanese z usually begins with the tongue touching the ridge behind the teeth, closer to dz. So learners often say then with a d-like start, which takes it even further from the soft English TH.

The confusion runs both ways. In a study by Iino and Wistner (2022), Japanese students took Z for this TH 42% of the time, and this TH for Z 16% of the time.

What to listen for

Listen for the hiss inside the buzz. Z has a bright, sharp hiss riding on the voice. The TH in then has almost none: it's mostly voice, soft and a little fuzzy.

At the start of a word, as in then and zen, TH is also very short and weak. In fast speech it can almost disappear, so listen for what's missing: no sharp hiss means TH.

At the end of a word, as in breathe and breeze, both sounds stretch out, which makes the difference easier to hear. In clothing and closing, only the sound in the middle differs.

When it matters: meaning

Mix them up and you get a different word. To breathe is to take in air, a breeze is a light wind. Clothing is what you wear, closing is shutting. To bathe is to wash, bays are inlets of the sea. To seethe is to boil with anger, to seize is to grab. To teethe is to grow first teeth, to tease is to make fun of someone.

The TH of then is also in some of the most common words in English: the, this, that, they, there. Hearing it clearly helps in almost every sentence.

How to practice hearing TH and Z

Use many voices. The TH in then is one of the quietest sounds in English, and speakers differ a lot in how strongly they make it, so many voices teach you to catch even a weak one.

Check every answer right away, keep sessions short, and go in order: pairs where the sound ends the word, like breathe and breeze, where it lasts longest, then clothing and closing, then pairs where it starts the word, like then and zen.

The TH in think and the S in sink are the voiceless version of this pair. TellApart has TH · S as a collection too.

How quickly you improve differs from person to person, so aim for short, regular sessions.