This section deals with situations in Korean, when the pronunciation does not follow the writing. All examples come from children's songs.
[1.1] What is a "batchim"?
"Batchim" refers to the consonant sound within a syllable that comes after the vowel. Korean has a vowel-centered syllable structure, i.e., the syllable is always structured as
an optional consonant + a mandatory vowel + a second optional consonant.
The second optional consonant in the formula above is called batchim.
[1.2] What are the sounds of "batchim"?
Although there are many different kinds of batchim in writing, there are only 7 possible sounds in actual prounuciation. These are:
[ㅂ],[ㄷ],[ㄱ],[ㄴ],[ㅁ],[ㅇ],[ㄹ].
[1.3] Single, double and compound batchim
There are three classes of batchim in writing: single, double, and compound. Single batchim consists of only one symbol, such as ㄱ and ㅎ. Double batchim consists of two repeated symbols, such as ㄲ and ㅆ. Compound batchim consists of two different symbols, such as ㄼ and ㅄ.
[1.4] Prounuciation rules for single and double batchim
Everything related to ㅂ (namely ㅂ and ㅍ, as ㅃ never appears as batchim) is pronunced [ㅂ].
Everything related to ㄷ (namely ㄷ and ㅌ, as ㄸ never appears as batchim) is pronunced [ㄷ].
Everything related to ㄱ (namely ㄱ, ㄲ and ㅋ) is pronunced as [ㄱ].
ㄴ,ㅁ,ㅇ,ㄹ are pronunced as themselves.
Everything else (within the realm of single and double batchim that is) is pronunced as [ㄷ]. These are: ㅅ, ㅆ, ㅈ, ㅊ and ㅎ.
[1.5] Pronunciation rules for compound batchim
The main rule: normally, the second symbol of a compound batchim is silent. But in ㄺ, ㄻ and ㄿ, it is the first symbol that is silent. When pronuncing the non-silent symbol, rules [1.4] apply. For instance, ㄿ is prounuced [ㅂ].
The exceptions to the main rule:
i) ㄺ. according to the main rule, it is pronunced as [ㄱ]. However, when it occurs at the end of a verb or adjective stem, and the ending that comes immediately after the stem starts with ㄱ, then the ㄺ is prounuced [ㄹ], with the following ㄱ intensified to [ㄲ].
For example:
ii) ㄼ. According to the main rule, it is pronunced as [ㄹ]. However, there are two words where complications occur.
ii-i) The first one is 밟다 (to step on). When its stem 밟- is immediately followed by an ending that begins with a consonant, the batchim ㄼ is prounuced as [ㅂ], and the following consonant is intensified. For example, the traditional Filipino game of a kid stepping on coconut shells (called "karang" in Tagalog) should be pronunced 코코넛 밟기[밥끼].
ii-ii) The second one is 넓다 (wide). When used by itself, the main rule is respected. However, when used in compound words, the batchim ㄼ is prounuced as [ㅂ]. For example, 넓죽하다[넙쭈카다] (wide and flat), 넓둥글다[넙뚱글다] (wide and round).
[2.1] What is liaison?
When a syllable that ends with batchim is followed by another syllable that starts with a vowel, the batchim tends to "jump over" to combine with the vowel. This is called liaison.
[2.2] Rules for liaison
When there is liaison, should we still apply the batchim pronunciation rules before the "jumpover"? Curiously, it depends on the meaning of the thing that comes after. If it referrs to something concrete, then the batchim rules should be applied. Otherwise, if it only carries grammatical significance, the batchim rules should not be applied.
For example:
[2.3] Liaison involving a composite batchim
If a vowel comes after a composite batchim, and the batchim pronunciation rules are not in effect (as per conditions outlined in [2.2]), then only the second symbol of the batchim combines with the vowel, whereas the first symbol remians within the previous syllable. Furthermore, if the second symbol is ㅅ, it will be intensified.
For example:
Here is a somewhat different example: 닭 앞에 (in front of a chicken) is pronunced [다가페]. Why? Because 앞 (front) is a word with concrete meaning, so the batchim pronunciation rules should first be applied to 닭 before the liaison occurs, which results in [닥]+앞에, that is, [다가페].
[3.1] What is assimilation?
When two sounds come together, changes may be triggered in one or both under mutual influence. The direction of change is for those two sounds to have more common characteristics. This is called assimilation. In Korean, there are three possible directions of assimilation: nasal, liquid and aspirated.
[3.2] Assimilation towards nasal sound (1)
When the a batchim is pronounced [ㄱ], [ㄷ], or [ㅂ], and is followed by nasal sounds, namely ㄴ or ㅁ, the batchim sounds themselves become nasalized. That is, [ㄱ] becomes [ㅇ], [ㄷ] becomes [ㄴ], [ㅂ] becomes [ㅁ].
Note that the position of pronunciation does not change in this process. For example, both [ㅂ] and [ㅁ] are pronounced with lips. To summarize,
[ㄱ] [ㄷ] [ㅂ] + ㄴ ㅁ -> [ㅇ] [ㄴ] [ㅁ] + ㄴ ㅁ.
Here are some examples:
[3.3] Assimilation towards nasal sound (2)
When a batchim pronunced [ㄱ], [ㄷ], or [ㅂ] is followed by ㄹ, not only does the batchim sound get nasalized, but the ㄹ also takes on a [ㄴ] sound. Namely,
[ㄱ] [ㄷ] [ㅂ] + ㄹ -> [ㅇ] [ㄴ] [ㅁ] + [ㄴ].
Very few examples can be found in children's songs, because this phenomenon mostly occurs in Chinese originated words that seldom gets used in children's songs. But here is one example:
[3.4] Assimilation towards nasal sound (3)
You might be wondering about the rule [3.3], because initially there are no nasal sounds, but after the sound change everything gets nasalized. It does seem a little bit strange. But here's another rule that might help you understand how [3.3] comes about:
ㅇ ㄴ ㅁ + ㄹ -> ㅇ ㄴ ㅁ + [ㄴ].
From [3.2], we already see that ㄱ, ㄷ and ㅂ tend to get nasalized BEFORE nasal sounds. Now [3.4] tells us that ㄹ tends to get nasalized AFTER nasal sounds. And when you put ㄱ, ㄷ and ㅂ before ㄹ, even without real nasal sounds initially, all of them nasalize under mutual influence, hence [3.3].
TODO: examples
Nota bene: there is an important caveat in rule [3.4] with ㄴ + ㄹ, which will be explained in [3.5].
[3.5] Assimilation towards liquid sound
Assimilation towards liquid sound happens only when ㄴ and ㄹ come together, regardless of order:
ㄴ + ㄹ -> [ㄹ] + ㄹ;
ㄹ + ㄴ -> ㄹ + [ㄹ].
For example:
Now we see that there are two possible ways of change when ㄴ is followed by ㄹ. The first way is
ㄴ + ㄹ -> ㄴ + [ㄴ] as per [3.4].
The second way is
ㄴ + ㄹ -> [ㄹ] + ㄹ as per [3.5].
Both of these occur, and one needs only to remember that the first way is limited in its scope. Without going into too much detail, let us just say that the first way only applies in a very limited set of Chinese originated words, where the ㄹ leads a syllable that corresponds to various Chinese characters of specific meanings, such as the "력" in 결단력[결딴녁](決斷力, meaning will to decide), and the "량" in 생산량[생산냥](生產量, meaning amount of output or yield). Children's songs normally don't have these words.
[3.6] Assimilation towards aspirated sound
When the symbol ㅎ is present immediately before or immediately after the consonant sounds [ㄱ], [ㄷ], [ㅂ] or [ㅈ], it will be assimilated INTO those sounds to make them aspirated: ㅋ, ㅌ, ㅍ and ㅊ. That is,
[ㄱ] [ㄷ] [ㅂ] [ㅈ] + ㅎ -> [ㅋ] [ㅌ] [ㅍ] [ㅊ];
ㅎ + [ㄱ] [ㄷ] [ㅂ] [ㅈ] -> [ㅋ] [ㅌ] [ㅍ] [ㅊ].
Note that the number of sounds decrease. There are many such examples in children's songs and here are some of them:
TODO: examples
While this section mainly deals with situations where pronunciation does not follow writing, it is worth mentioning some cases where the sound change IS reflected in writing. One of those is when the co-called "initial sound rules" come into play.
[10.1] What are initial sound rules?
Korean language, or more specifically the language that is standard in South Korea, is repellent towards "ㄹ" and "ㄴ" sounds at the beginning of a word. In particular,
1. The initial "ㄹ" sound always changes into "ㄴ".
2. If an "i" sound (e.g., ㅣ, ㅕ, ㅠ etc.) follows an initial "ㄴ" (which may or may not have been resulted from rule 1), the "ㄴ" drops.
For example, the word 역사, "history", should have been 력사, as can be seen from its Chinese equivalent, 歷史, which is pronunced as "lì shǐ". The ㄹ first changes into a ㄴ according to rule 1, then drops according to rule 2.
The Chinese originated word for "age", 연령 (which is equivalent to the native Korean word 나이), is a good example where only rule 2 applies. Here 연 comes from 년, "year", as in "2020년". The ㄴ drops because it is at the front of a word and is followed by an "i" sound.
Another example is the word 노동, "labour". Originally it should have been 로동, and the 로 has changed into 노 according to rule 1. Rule 2 does not apply here since the vowel coming after the ㄴ is "o" rather than "i". In North Korea the state newspaper is called "Labour News", or 로동신문, because the initial sound rules do not apply in North Korea. We refer you to the section "DPRK Children's Songs" and "Children's songs of ethnic Korean people in Yanbian" for more such examples.
[10.2] Exceptions to initial sound rules
Back to the standard South Korean language. There are 4 prominent exceptions to the initial sound rules outlined above. The first one is in loanwords that come from the west. Initial sound rules seldom apply to them. For example, 라디오, "radio"; "뉴스", news. The second exception is with numerical quantifiers 리(里), 년(年) and 냥(兩). These sould always be used in the form listed here.
There are also situations where the initial sound rules DO apply, while a literal interpretation of those rules would indicate otherwise. For instance, the second component of a compound word, like in 시골여행, "trip to countryside", functions like an independent word as long as these rules are concerned. Another more curious situation happens only with 렬 and 률. These become 열 and 율 even in the middle of a word, as long as they come after a vowel or a ㄴ sound. (Examples: 법률/운율, 행렬/수열.)