• As mentioned above, column four on the left has four sounds [yu, yue, yuan, yun], and all sounds are made with the lips rounded. It's actually quite fun to stand in front of a mirror and practice these sounds. The sounds themselves are not used in English, but they are actually quite easy to learn. The aggravating part is to figure out the spelling conventions that go with the lip rounding. This is a case where so-called "theoretical learning" goes a long way.

Point one:

The lip rounded finals are only preceded by five different initials in Chinese. They are: j, q, x, n, and l. That means, the total set of lip-rounded syllables in Chinese is quite small. Don't worry about the fact that you haven't learned the consonants in question here, but here are all of the lip-rounded syllables:

You will notice that in the chart above, that when "yu" and "yue" follow "n" and "l", the "u" is written with two dots: "ü." Why?
The lip-rounded finals only occur after j, q, x, n, and l. However, the final "wu" also occurs after "n" and "l" yielding "nu and lu," When "wu" occurs alone it is "wu," when preceded by an initial the "w" is dropped although.

Since "n" and "l" can be followed by both "wu" and "yu" we have:

To distinguish lip-rounding after "n" and "l," Pinyin uses u with two dots "ü" to signify the rounding. Therefore we have this solution:

And even though there is no spelling conflict with the sounds "nüe" and "lüe," they still carry the two dots which indicate lip-rounding.

After that long-winded explanation, the unmitigated poop which you MUST remember is that:

yu, yue, yuan, yun = lip-rounding

j, q, x before yu, yue, yuan, yun = lip-rounding, but the y is dropped. If you see two-dots ü after n and l it indicates lip-rounding.

Is there still source for confusion? Yes, and here it is. The people who designed Pinyin expect you to be smart enough to remember the y, j, q, x, two-dots ü rule. But three of the "w" sounds - "wu, wan, and "wen" - share spellings with the lip rounded sounds.

Bottom line, "u, uan, and un" are three instances of "one spelling two sounds." It is imperative that your remember "y, j, q, x, two-dots ü" means "fishbowl, fishbowl, fishbowl, fishbowl." If you don't incoporate this knowledge into your concept of Pinyin and pronunciation, you will be guilty of egregious Chinese - and even worse - incomprehensible Chinese.