Mandarin Yale was developed to prepare American soldiers to communicate with their Chinese allies on the battlefield. Rather than try to teach recruits to interpret the standard romanization of the time, the Wade-Giles system, a new system was invented that utilized the decoding skills that recruits would already know from having learned to read English, i.e. it used English spelling conventions to represent Chinese sounds. It avoided the main problems that the Wade-Giles system presented to the uninitiated student or news announcer trying to get somebody's name right in a public forum, because it did not use the "rough breathing mark" to distinguish between sounds like ''jee'' and ''chee''. In Wade-Giles the first of those would be written ''chi'' and the second would be written ''ch'i''. In the Yale romanization they were written ''ji'' and ''chi''. The Yale system also avoids the difficulties faced by the beginner trying to read pinyin romanization because it uses certain Roman letters and combinations of letters in such a way that they no longer carry their expected values. For instance, ''q'' in pinyin is pronounced something like the ''ch'' in ''chicken'' and is written as ''ch'' in Yale Romanization. ''Xi'' in pinyin is pronounced something like the ''sh'' in ''sheep'', but in Yale it is written as ''syi''. ''Zhi'' in pinyin sounds something like the ''ger'' in ''gerbil'', and is written as ''jr'' in Yale romanization. For example: in Wade-Giles, "knowledge" is ''chih-shih''; in pinyin, ''zhishi''; but in Yale romanization it is written ''jr-shr''—only the latter will elicit a near-correct pronunciation from an unprepared English speaker.
The tone markings from Yale romanization were adopted for pinyin.
Unlike the Mandarin Yale romanization, Cantonese Yale is still widely used in books and dictionaries for Standard Cantonese, especially for foreign learners. Developed by Parker Po-fei Huang and Gerald P. Kok, it shares some similarities with Hanyu Pinyin in that unvoiced, unaspirated consonants are represented by letters traditionally used in English and most other European languages to represent voiced sounds. For example, is represented as ''b'' in Yale, whereas its aspirated counterpart, is represented as ''p''. Because of this and other factors, Yale romanization is usually held to be easy for American English speakers to pronounce without much training. In Hong Kong, more people use Standard Cantonese Pinyin and Jyutping, as these systems are believed to be more localized to Hong Kong people .
* The finals ''m'' and ''ng'' can only be used as standalone .
There are nine tones in six distinct tone contours in Cantonese.
Cantonese Yale represents tones using tone marks and the letter ''h'', as shown in the following table:
* Tones can also be written using the tone number instead of the tone mark and ''h''.
* In modern Standard Cantonese, the high-flat and high-falling tones are indistinguishable and, therefore, are represented with the same tone number.
* Three entering tone: entering high-flat, entering mid-flat, entering low-flat have the same tone contours with high-flat, mid-flat, low-flat, but it have difference in which affect its short falling cadence only. So we use the same representation between three entering tones and flat tones.
Korean Yale was developed by Samuel Elmo Martin and his colleagues at Yale University about half a decade after McCune-Reischauer, and is still used today, although mainly by , among whom it has become the standard romanization for the language. The Yale system places primary emphasis on showing a word's morphophonemic structure. This distinguishes it from the other two widely used systems for romanizing Korean, the Revised Romanization of Korean and McCune-Reischauer. These two usually provide the pronunciation for an entire word, but the morphophonemic elements accounting for that pronunciation often can not be recovered from the romanizations, which makes them ill-suited for linguistic use. In terms of morphophonemic content, the Yale system's approach can be compared to a North Korean orthography known as Chos?n? sin ch'?lchap?p .
The Yale romanization represents each morphophonemic element by the same Roman letter, irrelevant of its context, with the notable exceptions of and which the Yale system always romanizes as ''u'' after bilabial consonants because there is no audible distinction between the two in many speakers' speech, and of the ''wu'' that represents in all other contexts.
The letter ''q'' indicates '''' which is not shown in hangul spelling:
* ''halq il'' /''hallil''/
* ''halq kes'' /''halkket''/
* ''kulqca'' /''kulcca''/
In cases of letter combinations that would otherwise be ambiguous, a period indicates the orthographic syllable boundary. It is also used for other purposes such as to indicate sound change:
* ''nulk.un'' “old”
* ''kath.i'' /''kachi''/ “together”; “like”, “as” etc.
A macron over a vowel letter indicate that in old or dialectal language, this vowel is pronounced :
* ''māl'' “word”
* ''mal'' “horse”
Note: Vowel length as a distinctive feature seems to have disappeared at least among younger speakers of the Seoul dialect sometime in the late 20th century.
A superscript letter indicates consonants that have disappeared from a word's and standard pronunciation. For example, the South Korean orthographic syllable is romanized as follows:
* ''yeng'' where no initial consonant has been dropped.
* ''lyeng'' where an initial l has been dropped or changed to n in the South Korean standard language.
Examples: ''lyengto''; ''lNo Muhyen''
* ''nyeng'' where an initial n has been dropped in the South Korean standard language.
The indication of vowel length or pitch and disappeared consonants often make it easier to predict how a word is pronounced in Korean dialects when given its Yale romanization compared to its South Korean hangul spelling.
There are separate rules for Middle Korean. For example, ''o'' means in a romanization of the current language, but for Middle Korean, where is transcribed as ''wo''. Martin 1992 uses italics for romanizations of Middle Korean as well as other texts predating the 1933 abandonment of ''arae a'', whereas current language is shown in boldface.