After you are comfortable with the six single-vowel finals, the next step is learning how Mandarin combines those sounds into compound finals. These are often called diphthongs, which means that within one syllable, your mouth moves or glides from one vowel position to another instead of staying fixed. This smooth movement is what gives Mandarin its natural flow.
The key idea is that you are not saying two separate vowels. Instead, you begin in one mouth shape and transition seamlessly into another, all within a single breath and a single tone.
Let’s start with ai. This sound begins with “a” (open mouth) and glides toward “i” (a more closed, front position). It is quite similar to the “eye” sound in English. The important thing is to start clearly on the open “a” before moving toward the “i,” rather than jumping straight to the end sound.
Next is ei. This begins with a mid, slightly open vowel and moves toward “i.” It resembles the “ay” sound in “say.” However, in Mandarin, the glide is usually tighter and more controlled, without exaggerating the ending.
The compound ao starts with “a” and glides toward “o.” It sounds somewhat like the “ow” in “cow.” Your mouth opens wide at first and then rounds slightly as you move to the second part of the sound.
Similarly, ou begins with a mid-back vowel and glides into a more rounded “u”-like ending. It is close to the “oh” sound in English, but again, Mandarin keeps it pure and smooth, without turning it into a long, changing vowel.
The finals iu and ui can be a bit confusing at first because their spelling does not fully show their underlying structure. iu is actually a contraction of “iou.” So the sound starts with an “i”-like position, briefly passes through an “o”-like middle, and ends with “u.” In practice, it sounds like a quick glide from “ee” to “oo.”
Similarly, ui comes from “uei.” It starts with a “u”-like rounding, moves through a mid vowel, and ends with “i.” It can sound a bit like “way,” but with more lip rounding at the beginning.
The compound ie begins with “i” and glides toward “e.” It resembles the “yeh” sound in English, as in “yes,” but smoother and more connected within one syllable.
The final üe combines the special vowel “ü” with “e.” This one requires careful mouth positioning: your lips stay rounded (as in “ü”), while your tongue moves toward the “e” position. It may feel unfamiliar, but once you master “ü” on its own, this combination becomes much easier.
Finally, er is slightly different from the others. Rather than a clear glide between two separate vowel positions, it has a unique r-colored sound. Your tongue curls slightly upward or backward, giving it a quality similar to the “er” in some English pronunciations of “her,” but it is more central and sustained. In Mandarin, this sound can also appear as a suffix (called erhua), influencing the pronunciation of whole words.
Mastering these compound finals greatly improves both your pronunciation and listening ability. Many Mandarin syllables rely on them, and being able to hear and produce the subtle differences between them will make your speech clearer and more natural.
That is all for lesson 3. See you again in lesson 4. If you have any questions about this lesson, post here in the forum.