What is the 3 3 3 rule in Chinese?

The 3-3-3 Rule in Mandarin: Mastering Tone Changes

When learning Mandarin, tones are everything. But even if you've memorized the four tones, there's a subtle yet essential rule that often trips up beginners: the 3-3-3 rule, more accurately known as the third-tone sandhi rule. This isn’t about repeating "3" three times—it’s a shorthand for how two third-tone syllables interact in speech.

Here’s the core idea: when two characters that both carry the third tone appear consecutively, the first one changes to a second tone. So instead of pronouncing both as low-dipping tones (3-3), you say them as rising then dipping (2-3). This makes speech smoother and more natural to native ears.

A classic example is 你好 (nǐ hǎo). While each character is individually third tone, when spoken together, the first syllable nǐ shifts to ní. So you end up saying “ní hǎo”—not “nǐ hǎo”—in natural conversation. It’s not an exception; it’s the rule.

This tone shift isn’t optional in fluent speech. Other examples include 很好 (hěn hǎo) → pronounced “hén hǎo” and 你买 (nǐ mǎi) → “ní mǎi.” Ignoring this can make your Mandarin sound robotic or disjointed.

It’s worth noting that this rule applies mainly to adjacent syllables. If there’s a pause or a break in rhythm, the change might not occur. Also, when three third tones appear in a row, things get more nuanced—sometimes only the first changes, sometimes the second, depending on phrasing.

Mastering the 3-3-3 rule isn't just about accuracy—it's about sounding natural. Like stress shifts in English (“desert” vs. “dessert”), these tonal changes are what give Mandarin its musical flow. So next time you say ní hǎo, remember: you’re not breaking the rules—you’re following them.