Unless otherwise noted, statements in this article refer to South Korean standard language based on the Seoul dialect.
Among younger generations, they may be just as aspirated as /pʰ, tʰ, tɕʰ, kʰ/ in initial position; the primary difference is that vowels following the plain consonants carry low tone.
[8] The IPA diacritic ⟨◌͈⟩, resembling a subscript double straight quotation mark, shown here with a placeholder circle, is used to denote the tensed consonants /p͈/, /t͈/, /k͈/, /t͈ɕ/, /s͈/.
Its official use in the Extensions to the IPA is for strong articulation, but is used in literature in the context of Korean phonology for faucalized voice.
Some works use full-size ʔ or small ˀ before tensed consonants; this notation is generally used to denote pre-glottalization.
Word-initial aspiration, intervocalic voicing, and higher pitch of the following vowels are shared qualities in Korean fricatives /s/ and /h/.
[14] There is free variation at the beginning of a word, where this phoneme tends to become [n] before most vowels and silent before /i, j/, but it is commonly [ɾ] in English loanwords.
/lb/ either reduces to [l] (as in 짧다 [t͡ɕ͈alt͈a] "to be short"[18]) or to [p̚] (as in 밟다 [paːp̚t͈a] "to step"[19]); 여덟 [jʌdʌl] "eight" is always pronounced 여덜 even when followed by a vowel-initial particle.
Most conceivable combinations do not actually occur;[b] a few examples are ⫽lh-tɕ⫽ = [ltɕʰ], ⫽nh-t⫽ = [ntʰ], ⫽nh-s⫽ = [ns͈], ⫽ltʰ-t⫽ = [lt͈], ⫽ps-k⫽ = [p̚k͈], ⫽ps-tɕ⫽ = [p̚t͈ɕ]; also ⫽ps-n⫽ = [mn], as /s/ has no effect on a following /n/, and ⫽ks-h⫽ = [kʰ], with the /s/ dropping out.
When the second and third consonants are homorganic obstruents, they merge, becoming fortis or aspirate, and, depending on the word and a preceding ⫽l⫽, might not elide: ⫽lk-k⫽ is [lk͈].
Korean consonants have three principal positional allophones: initial, medial (voiced), and final (checked).
The vowel that most affects consonants is /i/, which, along with its semivowel homologue /j/, palatalizes /s/ and /s͈/ to alveolo-palatal [ɕ] and [ɕ͈] for most speakers (see North–South differences in the Korean language).
In some dialects and speech registers, the semivowel /w/ assimilates into a following /e/ or /i/ and produces the front rounded vowels [ø] and [y].
[22] Incorrect application of these phonological rules, such as improper nasalization or assimilation, can significantly impair intelligibility for native speakers.
For instance, failing to apply nasalization rules correctly or not recognizing assimilation patterns can lead to pronunciations that are difficult for native speakers to understand, underscoring the importance of precise phonological training.
[23][24] The resulting geminate obstruents, such as [k̚k͈], [ss͈], [p̚pʰ], and [t̚tɕʰ] (that is, [k͈ː], [s͈ː], [pʰː], and [tːɕʰ]), tend to reduce ([k͈], [s͈], [pʰ], [tɕʰ]) in rapid conversation.
Hangul orthography does not generally reflect these assimilatory processes, but rather maintains the underlying morphology in most cases.
However, the data from one study suggests that while younger KCTV anchors try to produce them more or less distinctly, it is not clear whether that is learned or natural pronunciation, as they do so inconsistently.
In Gyeongsang dialect, /ɯ/ and /ʌ/ once have merged into [ə] in speech of older speakers, but they are distinct among young and middle-aged Daegu residents (they actually have the same vowels as Seoulites due to influence from Standard Korean).
[27][10][25] Korean used to have two additional phonemes, [ø] ㅚ and [y] ㅟ, but they are replaced by the diphthongs [we] and [ɥi] by the majority of speakers.
[10][25] Middle Korean had an additional vowel phoneme denoted by ᆞ, known as arae-a (literally "lower a").
The vowel merged with /a/ in all mainland varieties of Korean, but remains distinct in Jeju where it is pronounced [ɒ].
[citation needed] Some analyses treat /ɯ/ as a central vowel and thus the marginal sequence /ɰi/ as having a central-vowel onset, which would be more accurately transcribed [ȷ̈i] or [ɨ̯i].
The sequences /*jø, *jy, *jɯ, *ji; *wø, *wy, *wo, *wɯ, *wu/ do not occur, and it is not possible to write them using standard hangul.
The first syllable may have pitch as high as the second if it starts with a tense ㅃ, ㅉ, ㄸ, ㄲ, ㅆ /p͈, t͈ɕ, t͈, k͈, s͈/ or an aspirated ㅍ, ㅊ, ㅌ, ㅋ /pʰ, tɕʰ, tʰ, kʰ/ consonant, as well as ㅅ, ㅎ /sʰ, h/, or lower rising pitch if it starts with plain ㅂ, ㅈ, ㄷ, ㄱ /p, tɕ, t, k/ or a sonorant ㅁ, ㄴ, ㄹ /m, n, r/, including silent ㅇ, i.e. a vowel.
[11] As early as 2004, researchers have posited that pitch and voicing are the actual distinguishing features between modern Korean consonants rather than the standard but seemingly ill-defined "tense" vs "lax" theory.
[31] Kim Mi-Ryoung (2013) notes that these sound shifts still show variations among different speakers, suggesting that the transition is still ongoing.
[33] On the other hand, Choi Ji-youn et al. (2020) disagree with the suggestion that the consonant distinction shifting away from voice onset time is due to the introduction of tonal features, and instead proposes that it is a prosodically conditioned change.
For example, in trisyllabic words, there are four possible tone patterns:[34] The following changes have been observed since the mid-20th century and by now are widespread, at least in South Korea.
They depend on age and gender, the speech of young females tends to be most innovative, while old males are phonologically conservative.