Chinese tones guide
Chinese Tone Change Rules, Explained Simply
Mandarin tones shift in predictable ways when words meet — but pinyin does not write the shifts down, so you have to carry them in your head. The reassuring part: there are only four rules worth learning, and you have already met two of them in the word 你好.
First, why these rules exist at all
Tone sandhi — the technical name for these changes — is not Mandarin being awkward. It is the language doing what every language does: smoothing sounds that are hard to say back-to-back so that speech can flow at natural speed. Two low, creaky third tones in a row are genuinely clumsy to produce one after the other, so the language nudges the first one out of the way. Once you see the rules as shortcuts your mouth wants anyway, they stop feeling like arbitrary exceptions to memorize and start feeling like the path of least resistance.
The catch that makes them a learner's problem is a quirk of the writing system: pinyin marks the tone a syllable has on its own, not the tone it takes in context. So the page tells you one thing and a native speaker says another, with no written cue bridging the gap. That is why these rules cannot be read once and filed away — they have to become automatic in the mouth, because nothing on the page will ever remind you to apply them mid-sentence.
Rule 1: 3-3 becomes 2-3
When two third tones come in a row, the first one turns into a second tone. nǐhǎo 你好 is written with two tone-3 marks but spoken níhǎo, rising then low. This is the most famous sandhi rule, and the one you meet on day one whether or not anyone names it.
Longer strings need a little more thought. With three or more third tones in a row — 我也很好, "I'm well too" — speakers group the words by meaning and apply the rule inside each group, which is why the same string can be chunked more than one way. You do not need the full theory to be understood: as a practical fallback, changing every third tone except the last one to a second tone works fine in ordinary conversation and will never leave you unintelligible.
Rule 2: the half-third tone
When a third tone is followed by any other tone (1, 2, 4, or neutral), it loses its rising tail entirely: you drop low and stay there. This is not optional refinement or "advanced" pronunciation — it is simply how tone 3 is spoken most of the time, since it stands before another tone far more often than it stands alone. Because tone 3 is so central and so widely misunderstood, it has its own dedicated guide; the short version is that "low and flat" should be your default tone 3, and the textbook dip is the exception.
Rule 3: 不 bù changes before a fourth tone
不 (bù, "not") is normally a fourth tone. But when the syllable right after it is also a fourth tone, 不 shifts up to a second tone to avoid two sharp falls colliding: búshì 不是 (is not), búcuò 不错 (not bad). Before tones 1, 2, and 3, 不 keeps its ordinary fourth tone. Since 不 is one of the most frequent words in the language, this small rule fires constantly, and getting it right is a quick, high-value win.
Rule 4: 一 yī is a shape-shifter
一 (yī, "one") is the most changeable syllable of all, taking three different tones depending on what follows it:
- Alone or in numbers — first tone. yī 一, and in strings of digits like a year: 二〇二一.
- Before a fourth tone — second tone. yígè 一个 (one / a), where the following 个 is (a reduced) fourth tone, so 一 rises to dodge the clash.
- Before a first, second, or third tone — fourth tone. yìbēi 一杯 (one cup), yìqǐ 一起 (together).
There is a pattern hiding inside the list: like 不, 一 flips to a second tone specifically before a fourth tone, again to keep two falls from stacking. Notice that both "shifting" words move toward the tone that flows most easily into their neighbour — which is the whole logic of sandhi in miniature.
How to make the rules automatic
Reading these four rules takes five minutes. Making them happen at speaking speed, without a pause to compute, is the actual work — and it is a different kind of work, closer to a motor skill than to memorization. You cannot think your way through sandhi in real time; you have to have drilled the words often enough that the changed form is simply the form you produce.
The efficient way to build that reflex is to drill words and short phrases where each rule fires, and to have something confirm the change actually happened — that your 你好 really came out 2-3 and your 不是 really came out 2-4, rather than sliding back to the written tones. That "did it actually change?" check is hard to do for yourself, since the errors are exactly the ones your ear forgives; it is one of the clearest cases where recorded, AI-checked practice earns its keep. Gather the classic sandhi words — 你好, 很好, 可以, 不是, 不错, 一个, 一起, 一杯 — into a small deck, drill them until the changed forms feel like the only natural way to say them, and the rules stop being rules you recall and become simply how you talk.