Tone Sandhi in Mandarin Chinese

In Brief

Tone sandhi (变调, biàndiào) is a predictable change of tone caused by the surrounding sounds. Learn three patterns first: 3rd + 3rd becomes 2nd + 3rd, 不 bù becomes bú before a 4th tone, and 一 yī becomes yí before a 4th tone but yì before tones 1, 2, and 3. The characters do not change; only their pronunciation in context does.

Overview

Mandarin tones are often taught one syllable at a time: first tone is high and level, second rises, third is low or dipping, and fourth falls. Real speech is produced in phrases, however, not as a row of isolated dictionary entries. When certain tones meet, Mandarin adjusts them to make the phrase easier and more natural to pronounce. These regular adjustments are called tone sandhi.

Tone sandhi matters from A1 onward because it appears in extremely common expressions such as 你好 “hello,” 不是 “is not,” and 一个 “one; a.” It normally changes the spoken tone without changing the character or the word’s meaning. A learner therefore needs to keep two forms in mind: the underlying tone (the tone associated with the word and usually shown in a dictionary) and the surface tone (the tone actually heard in that particular phrase).

English uses pitch for emphasis, attitude, and sentence melody, but changing the pitch of one syllable does not usually create a different dictionary word. That makes it tempting for an English-speaking learner to treat these changes as optional expression. They are not: the major sandhi patterns belong to ordinary Mandarin pronunciation. The good news is that the beginner rules are few and highly predictable.

How It Works

1. Two third tones: 3 + 3 → 2 + 3

When two third-tone syllables occur together in one close phrase, the first is pronounced like a second tone:

3rd + 3rd → 2nd + 3rd

Thus 你好, whose dictionary forms are nǐ hǎo, is pronounced approximately ní hǎo. Likewise, 很好 hěn hǎo is spoken hén hǎo. The first syllable rises; trying to make two full dipping tones in succession sounds labored.

The changed syllable has the pitch shape of a second tone, but it remains a third-tone word in the learner’s mental vocabulary. That distinction matters when the word appears in another environment. For example, 你 is still learned as nǐ, not as ní.

Underlying sequence	Spoken pattern	Example
3 + 3	2 + 3	你好 nǐ hǎo → ní hǎo
3 + 3	2 + 3	可以 kě yǐ → ké yǐ
3 + 3	2 + 3	很晚 hěn wǎn → hén wǎn

2. A third tone before other tones: use the low form

A third tone is rarely a dramatic fall-and-rise in the middle of normal speech. Before a first, second, or fourth tone, it is commonly realized as a half third tone: a low tone that does not rise fully. This is a phonetic reduction (a regular change in how a sound is realized), rather than the 3 + 3 replacement rule.

In 老师 lǎoshī “teacher,” for example, 老 stays third tone but is normally kept low before the first tone of 师. In 很多 hěn duō “many,” 很 is low before 多. A full dipping-and-rising third tone is easiest to hear when the syllable is isolated, emphasized, or at the end of a phrase.

For beginners, the practical contrast is:

• before another third tone, make the first syllable rise like tone 2;
• before tones 1, 2, or 4, keep the third tone low and move on;
• at the end of a phrase, a fuller third-tone contour may appear.

3. 不: bù becomes bú before a fourth tone

The negative word 不 has the basic pronunciation bù (fourth tone). Immediately before another fourth-tone syllable, it changes to second tone, bú:

bù + 4th tone → bú + 4th tone

• 不是: bù shì → bú shì “is not”
• 不要: bù yào → bú yào “do not; do not want”
• 不去: bù qù → bú qù “not go”

Before tones 1, 2, and 3, 不 stays fourth tone: 不吃 bù chī, 不来 bù lái, 不好 bù hǎo. This rule depends on the next syllable’s tone, not on the English meaning of the phrase.

Following tone	Pronunciation of 不	Example
1st	bù	不吃 bù chī “not eat”
2nd	bù	不忙 bù máng “not busy”
3rd	bù	不好 bù hǎo “not good”
4th	bú	不看 bú kàn “not look”

4. 一 changes according to the following tone

The number 一 has the basic tone yī. When it directly modifies or precedes another syllable in a phrase, its tone usually changes as follows:

Environment	Pronunciation	Example
before 4th tone	yí (2nd tone)	一个 yí ge “one; one item”
before 1st tone	yì (4th tone)	一天 yì tiān “one day”
before 2nd tone	yì (4th tone)	一年 yì nián “one year”
before 3rd tone	yì (4th tone)	一起 yì qǐ “together”
alone, phrase-final, or in counting	yī (1st tone)	一、二、三 yī, èr, sān

A frequent surprise is 一个. The measure word 个 has an underlying fourth tone (gè), although it is often weakened to neutral tone in speech. 一 therefore takes the second-tone form: yí ge.

When 一 names the digit in a number, serial number, telephone number, date, or similar sequence, it commonly keeps first tone. It also keeps first tone in 第一 dì-yī “first,” where 一 is part of an ordinal expression. These uses identify the number rather than forming an ordinary “one + noun” quantity phrase.

What changes—and what does not

Tone sandhi changes pronunciation, not characters. Pinyin presentation varies by purpose: dictionaries and vocabulary lists often preserve underlying tones, especially in forms such as nǐ hǎo, while pronunciation-focused materials may display the spoken form ní hǎo. Do not assume that a pinyin spelling with the original mark tells you to pronounce every tone in isolation.

The safest study habit is to record both when needed: 你好 nǐ hǎo [spoken ní hǎo]. For 不 and 一, many learning materials write the changed pronunciation directly, but editorial conventions are not completely uniform.

Examples in Context

Mandarin	Spoken pinyin	English	Note
你好！	ní hǎo!	Hello!	3 + 3 → 2 + 3
他很好。	tā hén hǎo.	He is very well.	很 changes before 好
现在很晚。	xiànzài hén wǎn.	It’s very late now.	很 changes before 晚
我可以去。	wǒ kéyǐ qù.	I can go.	可 changes before 以
他不是老师。	tā bú shì lǎoshī.	He is not a teacher.	不 before 4th-tone 是
今天不要去。	jīntiān bú yào qù.	Don’t go today.	不 before 4th-tone 要
我不喝咖啡。	wǒ bù hē kāfēi.	I don’t drink coffee.	不 stays 4th before tone 1
这个不好。	zhège bù hǎo.	This isn’t good.	不 stays 4th before tone 3
我要一个。	wǒ yào yí ge.	I want one.	一 before underlying 4th-tone 个
我们一天学一课。	wǒmen yì tiān xué yí kè.	We study one lesson a day.	一 → yì before tone 1; yí before tone 4
她学了一年中文。	tā xuéle yì nián Zhōngwén.	She studied Chinese for one year.	一 → yì before tone 2
我们一起吃饭吧。	wǒmen yìqǐ chīfàn ba.	Let’s eat together.	一 → yì before tone 3
他是第一名。	tā shì dì-yī míng.	He is in first place.	一 stays yī in 第一
一、二、三，开始！	yī, èr, sān, kāishǐ!	One, two, three—start!	Isolated counting form

Common Mistakes

Pronouncing two full third tones

• Wrong: nǐ hǎo, with a full dip and rise on both syllables
• Right: ní hǎo
• Why: In a close 3 + 3 sequence, the first third tone changes to a rising tone. Save the third tone for the second syllable.

Changing every 不 to bú

• Wrong: bú hǎo for 不好
• Right: bù hǎo
• Why: 不 changes only before a fourth tone. 好 hǎo is third tone, so 不 remains bù.

Always saying yī for 一

• Wrong: yī tiān, yī nián, yī gè in ordinary connected speech
• Right: yì tiān, yì nián, yí ge
• Why: In quantity expressions, 一 adjusts to the following tone: yí before tone 4 and yì before tones 1–3.

Changing 一 inside every number

• Wrong: treating the 一 in a telephone number as though it modified the following digit
• Right: use the sequence-reading convention taught for digits, normally keeping 一 as yī (telephone digits often use yāo for 1 to avoid confusion)
• Why: A named digit is not the same grammatical use as “one + measure word + noun.”

Trusting tone marks without listening to the phrase

• Wrong: assuming written nǐ hǎo must be pronounced as two unchanged citation tones
• Right: learn the underlying spelling and the connected pronunciation together
• Why: Pinyin may preserve dictionary tones even where sandhi applies in speech.

Usage Notes

Tone sandhi is not restricted to casual slang. Careful speakers, teachers, and newsreaders all use the basic rules, although speech rate affects how fully each pitch contour is realized. In slow demonstration speech, a teacher may pronounce a word alone with its dictionary tone and then pronounce it differently inside a phrase.

Stress also matters. Unstressed syllables may become shorter and lighter, and a syllable written with a tone in a dictionary may approach neutral tone in a familiar expression. Sandhi and neutral tone are related aspects of connected pronunciation, but they are not identical: sandhi applies a predictable tone pattern, while neutral tone is an unstressed, context-dependent pitch whose exact height depends partly on the preceding tone.

Regional accents can realize pitch shapes differently. The rules in this article describe Standard Mandarin pronunciation. You may hear variation in the size of a rise or fall, but the major contrasts—especially 3 + 3 and the changes of 不 and 一—remain essential learning targets.

Beyond the Basics / Advanced Use

You do not need to master long tone chains at A1, but you will hear them immediately. With three or more consecutive third-tone syllables, the result is not produced by blindly changing every tone except the last. Speakers divide the utterance into meaningful rhythmic groups, and the grouping affects the pitch pattern. For example, 我很好 is naturally organized around 我 + 很好; the exact realization reflects both the third-tone sequence and that phrase structure. In longer expressions, different natural groupings can produce different patterns.

This is why a simple formula such as “3 + 3 + 3 becomes 2 + 2 + 3” is not a complete general rule. It may describe some tightly grouped words, but syntax (how words form phrases), meaning, emphasis, and speaking rate all influence longer chains. At an advanced level, practice whole phrases with reliable audio rather than calculating each syllable separately.

一 also has a reduplication pattern in which it appears between repeated verbs, as in 看一看 “take a look” or 想一想 “think it over.” In this weak, short use, it is often pronounced lightly or with a neutralized tone rather than as a prominent full yī. Similarly, 不 can become light in familiar A-not-A questions such as 是不是？ “is it or isn’t it?” The beginner rules still provide the foundation, but natural stress can reshape very weak syllables.

Finally, tone sandhi does not erase lexical identity. A changed third tone may sound similar to an underlying second tone in that moment, yet native listeners recover the word from the phrase. Keeping underlying tones in your vocabulary notes helps you predict what happens when the same word enters a different environment.

Practice Tips

1. Practice in pairs, not isolated syllables. Alternate 你好—不好, 不是—不来, and 一个—一天. Say the second syllable’s tone first, then choose the correct form of the first.
2. Mark underlying and spoken tones differently. Write nǐ hǎo → ní hǎo and yī gè → yí ge. This prevents you from relearning the dictionary form incorrectly.
3. Shadow short recordings. Listen to one complete phrase, copy its rhythm and pitch, record yourself, and compare. For long third-tone sequences, imitation is more reliable than applying a formula syllable by syllable.

Related Concepts

• Prerequisite: The Four Tones — review the four lexical tones and neutral tone before practicing contextual changes.