Third-Tone Sandhi (你好 → ní hǎo)

Some of the very first words you learn in Mandarin hide a pronunciation rule that the spelling flatly refuses to show you. 你好 — "hello," the first thing anyone teaches you — is written nǐ hǎo, with two 3rd-tone marks, but nobody actually says it that way. It comes out ní hǎo, with the first syllable rising like a 2nd tone. This is third-tone sandhi: when one 3rd tone is immediately followed by another 3rd tone, the first one changes into a 2nd (rising) tone. It is the most common tone change in the language, it happens automatically in native mouths, and — because pinyin does not write it — you have to learn to apply it yourself. Master this one rule and a huge amount of everyday Mandarin instantly sounds right. ("Sandhi," pronounced SAN-dee, is the linguists' word for a sound that changes because of its neighbours.)

The rule: 3rd + 3rd → 2nd + 3rd

Two low, dipping tones back to back are awkward to say — your voice would have to sink to the bottom, climb, sink again, and climb again. Mandarin resolves the clash by lifting the first syllable up into a clean rising tone. The second 3rd tone is unchanged. So:

The transformed first syllable is a real, full 2nd tone — it climbs all the way up, exactly like the rising tone in any other word. It is not a half-hearted lift. If you only give it the low "half-third" you learned for 3rd tones before other tones, the sandhi hasn't happened.

The pinyin is lying to you (on purpose)

Here is the point that trips everyone up: standard pinyin does not mark third-tone sandhi. It keeps the underlying tones — the ones the words have when you look them up in a dictionary — and leaves it to the speaker to apply the change. So 你好 is forever written nǐ hǎo, even though the nǐ is a fiction the moment you open your mouth.

This is a deliberate design choice: the spelling shows you the word's "citizenship" (its real, stored tone) so you can recognise it, while trusting you to run the sandhi rule live. Once you know the rule, the written nǐ is simply a reminder that this is underlyingly a 3rd tone that happens to be sitting before another one.

Longer strings: grouping decides

When three or more 3rd tones line up, the sandhi still applies, but the outcome depends on how the words group into meaningful chunks — because sandhi runs inside a chunk, and the boundary between chunks resets it. The everyday example is a full sentence built from all 3rd tones:

Here the natural grouping is 我 | 很好. Inside 很好 the first syllable rises (hén hǎo); the leading 我 stays a low half-third. A different grouping would give a different result, which is why native speakers rely on meaning, not on counting syllables. Now extend it:

Don't over-analyse these while speaking. In practice, apply sandhi within each little word or tight phrase and let the pauses take care of the boundaries. The two-syllable cases (你好, 很好, 可以) cover the vast majority of what you will actually say, so nail those first.

Why English speakers find this manageable

Good news: sandhi is not a foreign idea to you. English does the same kind of automatic reshaping constantly — you say "input" with the n creeping toward an m sound before the p, and you turn "t" into a flap in "water," all without thinking. You already run live sound rules that the spelling ignores. Third-tone sandhi is exactly that: an automatic adjustment triggered by the next sound, invisible in writing. The only new part is which adjustment (3rd → 2nd) and when (before another 3rd). Treat it like the flapped t — a reflex to build, not a fact to recite.

Common Mistakes

1. Saying both syllables as full dipping 3rd tones. The untrained instinct is to honour both tone marks: nǐ (dip) … hǎo (dip). It is slow, effortful, and unmistakably foreign. The whole point of the rule is to spare you that double dip.

2. Under-doing the rise into a half-third. Some learners know "something changes" and just flatten the first syllable low instead of raising it. But sandhi turns it into a full rising 2nd tone — commit to the climb.

3. Trying to write the change. Some learners "correct" the spelling to ní hǎo. Don't — standard pinyin keeps the underlying nǐ hǎo. The change lives in your mouth, not on the page. (This is the opposite of the 不 rule, whose sandhi is usually written — a contrast worth remembering.)

4. Applying sandhi across a real pause. If a 3rd tone ends a phrase and the next 3rd tone starts a new one after a break, the collision is gone and no sandhi happens. Sandhi needs the two syllables to actually run together.

5. Not automating it. Working the rule out consciously, syllable by syllable, mid-conversation is too slow. Drill the common pairs until ní hǎo and hén hǎo come out without a thought.

Key Takeaways

• 3rd + 3rd → 2nd + 3rd: the first of two adjacent 3rd tones becomes a full rising 2nd tone.
• 你好 is written nǐ hǎo but said ní hǎo; 很好 → hén hǎo.
• Pinyin keeps the underlying marks and does not show the change — you apply it live.
• In longer strings, grouping into meaning chunks decides where the sandhi lands (我 | 很好 → wǒ hén hǎo).
• This is the most important sandhi to automate early — drill the common two-syllable pairs into a reflex.