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Third Tone Sandhi: The Chinese Tone Change Rules Explained

ChinesePath · Updated September 5, 2026

Third tone sandhi is the rule that changes how Mandarin's third tone is actually pronounced: when a third-tone syllable is followed by another third tone, it is pronounced as a second (rising) tone. So 你好 is written nǐ hǎo but pronounced ní hǎo. Before any other tone, the third tone is cut down to a "half third tone" — just the low falling part, with no rise at the end. The pinyin spelling never changes; only the pronunciation does.

That is the whole system in two sentences. The rest of this guide explains each rule with examples, covers the three-syllable cases, and shows you the single insight that fixes most learners' third-tone problems.

What is the third tone supposed to sound like?

In isolation, the Mandarin third tone is described with the pitch contour 214: your voice starts fairly low (2), dips to the very bottom of your range (1), then rises (4). Say 演 yǎn alone and you produce the full dip-and-rise.

But here is the fact most textbooks underplay: the full 214 contour is the exception, not the rule. You only hear it when the syllable stands alone or ends a phrase. The moment a third-tone syllable is followed by anything else — which is most of the time in real speech — it changes.

Rule 1: Third tone + third tone → second tone + third tone

When two third-tone syllables come together, the first one is pronounced as a second tone:

Why does Mandarin do this? Two full third tones in a row are physically awkward. The third tone is already the longest, most effortful tone — sink to the bottom, then climb back up. Doing that twice back to back breaks the rhythm of speech. Native speakers solved it naturally: turn the first dip into a smooth rise (35), which flows perfectly into the following fall. One rise, one fall — that is the smoothest possible sequence.

Note that this change is completely mandatory. There is no register of Mandarin, formal or casual, where 你好 is pronounced with two full third tones.

Rule 2: Third tone + any other tone → half third tone

When a third-tone syllable is followed by a first, second, or fourth tone (or a neutral tone), it keeps its third-tone identity but loses the final rise. You pronounce only the low falling part: 21 instead of 214. This is called the half third tone (半三声).

In running speech, more than 80% of all third tones are pronounced as half third tones. Rule 1 covers most of the rest. The full 214 contour survives only at the end of a phrase or in isolated syllables.

What about three third tones in a row?

Words and phrases like 展览馆 (exhibition hall) or 我很好 (I'm fine) stack three third tones. The pronunciation depends on which two syllables group together in meaning:

Another 1 + 2 example: 纸老虎 zhǐlǎohǔ (paper tiger) is pronounced zhǐ láo hǔ, with 纸 as a half third tone because 老虎 is the tight unit.

You do not need to compute this consciously. If you learn words as chunks — 展览 as one unit, 老虎 as one unit — the grouping comes for free.

Why do learners get the third tone wrong?

Here is the insight that untangles the whole tone-3 problem: lowness is the essence of the third tone, not the dip-and-rise shape.

Compare the four tones by their core feature:

A Mandarin listener's brain identifies the third tone by one cue: the pitch drops to the very bottom. The final rise (the "4" of 214) is decorative — real speech omits it more than 80% of the time, and nobody misunderstands.

Many learners — English speakers especially — struggle because they try too hard to perform the rise. The result is an overcooked contour like 2135 that listeners hear as a second tone, which is precisely the wrong tone. The fix is the opposite of more effort:

Press your pitch as low as it will go, and don't worry about coming back up. If your voice truly reaches the bottom, a flat low syllable is already a correct third tone.

Does pinyin spelling change when the tone changes?

No — never. Pinyin always writes the original (dictionary) tone: 你好 is always written nǐ hǎo, even though everyone says ní hǎo. Tone sandhi lives only in pronunciation. This convention protects you when reading: the written tone mark tells you what the syllable fundamentally is, and the sandhi rules tell you how to say it in context.

The same principle applies to the other Mandarin tone changes — the shifting tones of 一 (yī) and 不 (bù), which follow their own rules.

Frequently Asked Questions

Is third tone sandhi optional in casual speech?

No. It is mandatory in every register of Mandarin. Pronouncing 你好 as two full third tones is not "extra careful" — it is simply wrong, and it sounds unnatural to native speakers.

Do tone marks in pinyin show the changed tone?

No. Pinyin always writes the original tone (nǐ hǎo), and the change happens only in speech. Dictionaries, textbooks and this site all follow this convention.

How is the changed third tone different from a real second tone?

Acoustically they are essentially the same rise (35). In 你好, the syllable nǐ is pronounced like ní. The difference is purely in the writing system and in the word's identity — which matters when the following word changes and the syllable reverts to its low third tone.

What is a half third tone?

A third tone pronounced as only its low falling part (pitch 21), with the final rise omitted. It occurs whenever a third tone is followed by a first, second, fourth or neutral tone — which makes it the most common realization of tone 3 in real speech.

Why does my third tone sound like a second tone?

You are probably rising too much at the end. Lowness, not the rise, is what identifies tone 3. Keep the syllable low — sink to the bottom of your pitch range and stay there — and listeners will hear a correct third tone.