pronouncekit

PRONUNCIATION RULE

yī · bù: tone changes of yī and bù

Learn how 一 and 不 change tone: bù becomes bú before a fourth tone, and yī shifts to yí or yì depending on what follows.

yī · bù

Mouth & tongue

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Vocal folds: vibrating

TongueTeethUvula

Simplified human pronunciation. The small uvula hangs from the palate; it is not the vocal folds. The wave indicates voicing.

Sound to demonstrate
Tone

High and level, around 55 on the five-level pitch scale.

Voice settings

The mouth starts slightly open. Movement is slowed for observation; the synthetic sound plays once at its original speed. Pause holds the current mouth shape; reset returns to the relaxed position. The panda is a symbolic teaching aid for human pronunciation, not animal anatomy. A simplified teaching model, not a measured or anatomically validated simulation. It shows the soft palate lowering for nasal sounds, but not airflow. Single syllables use eSpeak NG, a synthetic voice on your device. Its pitch range is narrower than natural speech, so use the tone diagrams and word buttons as well. Words and sentences use a voice from your browser or device when one is available. No native recordings are bundled.

Words to practice

Sentence to practice

Listen and compare

Each pair starts with the same character, and the following tone changes how it is said.

Pinyin here shows dictionary tones. Spoken tones change in some contexts, such as nǐ hǎo; see the lessons on tone changes.

What you are learning

Two very common words change tone with what follows. Textbooks often print the spoken tone; dictionaries print the original one. On this site the word lists show dictionary tones, so use this rule when you read them.

What your mouth is doing

Bù keeps its falling tone except before another fourth tone, where it rises: bú shì. Yī is first tone when counting, at the end of a phrase, and in ordinals and dates: dì-yī, yī yuè. Before a fourth tone it rises, yí gè; before other tones it falls, yì tiān.

Compared with English

English has no comparable rule. It helps to memorize frequent chunks, such as bú shì, yí gè and yì diǎn, instead of working them out while you speak.

Build the sound, step by step

  1. Say bù hǎo with a fall and bú shì with a rise.
  2. Count yī, èr, sān with a level first tone.
  3. Say yì tiān, yì nián, yì diǎn and yí gè.

What to watch for

  • Saying bù shì with two falls sounds stiff and foreign.
  • Applying these rules to other words: only these two change in this way.

Related lessons

Keep practicing

References & editorial notes

PronounceKit wrote this lesson as practical guidance for English speakers, based on the references below. The comparisons are editorial teaching suggestions. It describes common Mainland Standard Mandarin patterns, not every accent or regional variety, and it has not been independently reviewed by a pronunciation specialist or Mandarin teacher.

Published 5 November 2026