"zh," "ch," and "sh" are sometimes referred to as "retroflex" because they are pronounced with the tip of the tongue curled (or raised) to touch the roof of the mouth (for "zh" and "ch"), or close to (but not touching) the roof of the mouth (for "sh.")
The difference between "zh" and "ch" lies in aspiration. "zh" is unaspirated (without air coming out of the mouth) whereas "ch" is aspirated (with air coming out of the mouth). (See the difference between "q" and "j" in Unit 4.)
When "zh," "ch," or "sh" is followed by "i" (in spelling), the "i" is not pronounced as a regular "i," but is only used to bring the quality of a vowel to "zh," "ch," or "sh." This means neither the lip shape nor the tongue position will change when "i" is added to the "zh," "ch," or "sh" sound .
zhī, zhí, zhǐ, zhì; chī, chí, chǐ, chì; shī, shí, shǐ, shì
"ch" and "sh" can be compared to, but should not be confused with, "ch" and "sh" in English since "ch" and "sh" in English shares similarities to "q" and "x" in Chinese as well. (See Unit 4.) Similarly, "zh" can be compared to, but should not be confused with "j" in English.
Since "zh," "ch," and "sh" are never followed by a regular "i" or "ü" an important difference between "ch"/"sh" in Chinese and "ch"/"sh" in English lies in the fact there is never a hint of "i" after "zh," "ch," or "sh." For example, "shoo" in English and "shu" in Chinese are not the same.
shū, shú, shǔ, shù
"e" in the compound final "üe" is pronounced differently from when "e" is pronounced as a stand-alone vowel (a simple final). See Unit 1 for the pronunciation of "e."
"e" in "üe" is pronounced the same way it is pronounced in "ie;" that is, the position of the tongue is not as close to the roof of the mouth as when "e" is a simple vowel. (See Unit 4.) yuē, yué, yuě, yuè
When "ie" is not following an initial, it is written as "yue." The diacritic (the two dots on top of "u") should not be used.
"ong" is the combination of "o" and "ng." See Unit 1 for the pronunciation of "o."
It is important to round the lips when pronouncing "ong." The pronunciation of "ong" in Chinese should not be confused with that of "ong" in English. For example, "long" in Chinese and "long" in English are pronounced differently.
lōng, lóng, lǒng, lòng
