Tone Change Rules for the Chinese Word 一 (yī)

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*PLEASE NOTE*: This is the second post in our series on Tone Change Rules. If you haven't already, first check out our post detailing the tone change rules for the character 不 (bù).

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When starting to learn Chinese, you should start out by mastering pinyin and the tones so you have a solid foundation for pronunciation. 

Trust me, you'll want to focus on this right at the start - it's REALLY hard to go back and try to learn the correct tones after you've acquired a ton of vocabulary!

After learning pinyin and tones, you'll start learning words. One of the first few words you’ll learn in Chinese is 一 (yī), the one-stroke Chinese character, meaning... well, “one”. Another one you’ll soon learn is 不 (bù), which means “no” or “not”. Simple enough, right?

 
Well, as you’ll learn in our Beginner Conversational Course, 一 (yī) and 不 (bù) are tone-changing characters that you should pay special attention to.
 

There are four tones in Chinese, and technically a fifth tone: the first tone (high/flat), the second tone (rising), third tone (low/flat) and fourth tone (falling), and the fifth “neutral” tone (toneless tone).

*** If you're just getting started learning tones, or have struggled with tones in the past, stop right here and watch this live hangout where Yangyang teaches you how to master these tones: 

 
Now, in colloquial Chinese 一 (yī) can be pronounced as the first, fourth, second, or neutral tone, depending on its role and what context it’s in.
 
Many students that asked us about the tone changing rules for 一 (yī), so we decided to share these rules in a blog post to set the record straight!

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#1: First Tone (yī)

If it’s part of a general number, an ordinal number, an address, a time or a date, 一 (yī) should be pronounced as the first tone:

 
• 第一 (dì yī) - first 
• 一零一 (yī líng yī) - 101 (“one oh one”, not “one hundred and one”)
• 中山路一零二号 (zhōng shān lù yī líng èr hào) - No. 102 Zhongshan Rd.
• 一点 (yī diǎn) - 1:00 
• 周一 (zhōu yī) - Monday
• 一月 (yī yuè) - January
 

If it’s the last character in a word, it should also be the first tone:

• 万一 (wàn yī) - if by any chance
• 唯一 (wéi yī) - only
• 统一 (tǒng yī) - to unite

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#2: Fourth Tone (yì)

If it’s part of a word or phrase and 一 (yī) isn’t the last character of the word/phrase, it’s the fourth tone:

• 一点儿 (yì diǎnr) - a little

• 一起 (yì qǐ) - together
 
If it’s used with a measure word or a digit of a number ABOVE 99, it’s the fourth tone:

• 一杯水 (yì bēi shuǐ) - 1 cup of water

• 一瓶啤酒 (yì píng pí jiǔ) - 1 bottle of beer
• 一百块钱  (yì bǎi kuài qián) - 100 yuan

* Please note: If the 一  (yī) occurs as a digit BELOW 99, that digit is pronounced as the first tone. See how the tones differ between each occurrence of 一  (yī) in the below examples:
 
• 一百一十三 (yì bǎi yī shí sān) - 113
• 一千一百一十一 (yì qiān yì bǎi yī shí yī) - 1,111

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#3: Second Tone (yí)

This rule is very similar to the tone change rule for 不 (bù). If 一 (yī) should be the fourth tone, but it’s followed by another fourth tone character, 一 (yī) changes to the second tone:

 
When it’s part of a word or phrase and 一 (yī) isn’t the last character of the word/phrase:

• 一样 (yí yàng) - same/the same

• 一定 (yí dìng) - definitely
 
When 一 (yī) is used with a measure word or a digit of a number ABOVE 99:

• 一块钱 (yí kuài qián) - 1 dollar/RMB

• 一次 (yí cì) - 1 time
• 一万 (yí wàn) - 10,000

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#4: Neutral Tone (yi)
 
一 (yī) can also be pronounced as the neutral tone. The rule is a bit similar to the rule for 不 (bù) - basically when 一 (yī) is in the middle of a certain structure or phrase.
 
If 一 (yī) is used in between verbs in the structure "Verb + 一 (yi) + Verb", it’ll be pronounced as the neutral tone:
 
• 看一看 (kàn yi kàn) - to take a look, to look around
• 想一想 (xiǎng yi xiǎng) - to think about, to think it over
• 走一走 (zǒu yi zǒu) - to take a walk, to walk around

This next one is a bit tricky! If 一 (yī) is used in the middle of a verb phrase with a measure word, it can be pronounced as the neutral tone:

• 看一眼 (kàn yi yǎn) - take a look
• 说一声 (shuō yi shēng) - say
• 吃一口 (chī yi kǒu) - have a bite

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That wraps up the list of tone changes for 一 (yī) in colloquial Chinese. Please note that these tone changes aren’t always noted in written pinyin, so keep this as a guide that you can refer back to as needed!

These changes can be pesky, but don’t stress about sitting down and memorizing them all! Focus on the most common changes, like the 2nd and 4th tone changes for both characters. As a general rule, you can also associate the original first tone for 一 (yī) is used for mostly number-related language, with the exception of numbers above 99. 

Remember, the more you see (and hear) these tone changes in set phrases, the more comfortable you’ll be with using these tones changes when you’re speaking. With more practice listening to and speaking them in action, you’ll even find yourself saying the correct tones with the tone changes just from repetition, without even realizing it or thinking about the rules! 

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