In connected speech some tones change depending on the tone that follows. These changes are called tone sandhi. There are three rules that cover almost everything a learner meets.
Dictionaries, including hanzi.ac, write each syllable with its original tone. The changes below happen in speech; you apply them when you read the pinyin aloud.
Rule 1: two third tones in a row
When a third tone is followed by another third tone, the first one is said as a second tone.
| Written | Said | Word |
|---|---|---|
| nǐ hǎo | ní hǎo | 你好 hello |
| shuǐ guǒ | shuí guǒ | 水果 fruit |
| hěn hǎo | hén hǎo | 很好 very good |
With three third tones in a row, the grouping of the words decides which syllables change; in most cases the first two become second tones.
A related point: a third tone before a first, second, fourth or neutral tone is usually said as a “half third tone” — just the low part, without the rise at the end. Only a third tone at the end of a phrase, or said slowly on its own, has the full dip and rise.
Rule 2: the tone of 一 (yī, “one”)
一 is yī (first tone) when it stands alone, when counting, at the end of a word, and in dates and numbers. Otherwise:
- Before a fourth tone it becomes yí: 一个 yí gè (one of), 一定 yídìng (certainly).
- Before a first, second or third tone it becomes yì: 一天 yì tiān (one day), 一年 yì nián (one year), 一起 yìqǐ (together).
- Between two identical verbs it is neutral: 看一看 kàn yi kàn (have a look).
Rule 3: the tone of 不 (bù, “not”)
不 is bù (fourth tone), except:
- Before another fourth tone it becomes bú: 不是 bú shì (is not), 不对 bú duì (not right).
- In the middle of some three-syllable expressions it is neutral: 对不起 duìbuqǐ (sorry), 看不见 kàn bu jiàn (can’t see).
Why dictionaries don’t write the changed tone
Writing the original tone keeps each character’s reading constant, so 一 is always yī and 不 always bù whatever follows. Some textbooks do mark the changed tones for beginners, so you may see both spellings.
See also: the four tones.