This is 사잇소리. Basically, it's a phonetic phenomenon occurs in some compound nouns; a consonant is inserted in between two parts of the compound. (i.e. 주가
is considered as a compound 주(식)
+ 가(격)
, while 효과
is not.)
Korea Standard Language describes three conditions for 사잇소리. They are NOT rules, as they are just being descriptive and furthermore not every compound noun that fits into one of these conditions gets 사잇소리.
- When the following noun starts with 'ㄱ', 'ㄷ', 'ㅂ', 'ㅅ', 'ㅈ', they become fortis.
주 [주]
+ 가 [가]
-> [주까]
- Some speakers insert /t/ as well in between:
주-가 [줃까]
- When the following noun starts with 'ㄴ', 'ㅁ', /n/ is inserted in between.
- When the following noun starts with '이', double /n/ are inserted in between.
나무 [나무]
+ 잎 [입]
-> [나문닙]
- If the precoding noun has its own coda, only a single /n/ is inserted:
꽃-잎[꼰닙]
- Note that
꽃[꼳]
pronounced 꽃[꼰]-
because of consonant assimilation, not by a double insertion.
Related to this, there's an orthographical regulation, 사이시옷, which tries to use 'ㅅ' to explicitly spell out 사잇소리: 사이
+ 소리
-> 사잇소리[사이쏘리]
, 배
+ 머리
-> 뱃머리[밴머리]
, and 나무
+ 잎
-> 나뭇잎[나문닙]
. Only South Korean 맞춤범 uses 사이시옷 (see article 30 here).
There are a lot of exception cases in the 사이시옷 regulation,
- not only because the phonetic phenomenon it's originating is not strictly applied to all cases
- you might have noticed that
사이시옷
does not get 사이시옷, as it is not pronounced *[사이씨옫]
,
- but also the regulation itself introduces many other exceptional rules
- e.g. no Hanja-words combinations get 사이시옷, as in
주가(株價)
vs *줏가
, except for these six cases 곳간(庫間)
, 셋방(貰房)
, 숫자(數字)
, 찻간(車間)
, 툇간(退間)
, 횟수(回數)
.
This causes huge confusion in the everyday writings of normal people, and the regulation still gets fierce criticism from many Korean linguists even after many revisions.