一 yī / yí / yì

一 is yī on its own, yí before a fourth tone, yì before the other tones

What it means

一 (one) changes its tone with the syllable after it: yī on its own, yí before a fourth tone, yì before the other tones.

How it is built

一 + 4th tone → yí: 一对 yí duì (a pair). 一 + 1st, 2nd or 3rd tone → yì: 一天 yì tiān (one day). Alone → yī.

When to use it

Keep yī on its own, when you count (一、二、三), at the end of a number (十一), in 第一 (first) and in 一月 (January). Change it in phrases like “one day” (一天) or “a pair” (一对).

Watch out

Don't say yī everywhere. Next lesson you will say 一个 all the time, and it is yí ge, because 个 is really a 4th tone (gè).

Examples

Also in this lesson

• 三声 + 三声
• 不 bù / bú
• 儿化 · -r