For example, if I have the idiom:


Does the tone of the 一 change to a second tone because 路 is fourth tone?

  • Simply put, yes. Tone changing rules are universal applied. I can't think of any situation where tone changing rules are ignored.
    – NS.X.
    Oct 28, 2017 at 18:11

1 Answer 1


Yes it should be pronounced as the 2nd tone because it's put before character with the 4th tone. The sandhi rule applies with idioms too.

The cases should be pronounced as the 1st tone, i.e. shouldn't change the tone, are listed as the follows:

  1. 单独念时。如:一,一、二、三
  2. 用在一词或一句的末尾。如:统一祖国,唯一条件,单一成分,表里如一,不论三七二十一
  3. 表示年、月、日。如:1911年1月1日,一二•九运动,九•一八事变
  4. 表示序数。如:第一村,第一名,第一等,第一位

(1. when used alone; 2. when used at the end of the word or sentence; 3. when used in date; 4. when used as ordinal number with the meaning "first".)


(Under the above circumstances, no matter what the following character's tone is, should keep its original tone (i.e. the 1st tone) and doesn't change.)


  • 1
    @Belphegor It'll change to the 4th tone because 张 is pronounced as the 1st tone. Is the 4th case listed making you confusing about that? It's used as the numeral in 一张, that's different with the 4th case listed.
    – user4072
    Oct 29, 2017 at 8:11
  • I’m a bit confused about 2nd case where it says at end of the word. Not sure what would qualify as being at the end of the word. The example I gave with 张 I thought it was at the end of the word? Just now sure how to identify.
    – Belphegor
    Oct 29, 2017 at 17:30
  • I’m mainly confused about 唯一条件,单一成分, so those don’t change because it’s end of sentence or something ? How do you identify the “end”?@songyuanyao
    – Belphegor
    Oct 29, 2017 at 17:48
  • 1
    @Belphegor 唯一条件 could be seperated as 唯一 + 条件, i.e. 唯一 (and 单一) is an independent word and 一 is at the end of it. 一张 is different, 一 is used as the numeral, with the measure word 张 forms the word 一张, and then 一 is not at the end of the word.
    – user4072
    Oct 30, 2017 at 0:29
  • Ohhh, that makes a lot more sense now. Thank you!
    – Belphegor
    Oct 30, 2017 at 17:33

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