The new system corrected problems in the McCune–Reischauer system, such as phenomena where different consonants and vowels became indistinguishable in the absence of special symbols. To be specific, under the McCune–Reischauer system, Korean consonants "ㄱ(k), ㄷ(t), ㅂ(p) and ㅈ(ch)" and "ㅋ(k'), ㅌ(t'), ㅍ(p') and ㅊ(ch')" became indistinguishable when the apostrophe was removed. In addition, Korean vowels "어(ŏ)" and "오(o)" and "으(ŭ)" and "우(u)" became indistinguishable when the breve was removed. Especially in internet use where omission of apostrophes and breves is common, this caused many Koreans as well as foreigners confusion. Hence, the revision of the Romanization of Korean was made with the belief that if the old system was left unrevised, it would continue to confuse people, both Koreans and foreigners.
These are notable features of the Revised Romanization system:
ㄱ, ㄷ, ㅂ, and ㅈ have been changed from k, t, p, and ch to g, d, b, and j.
In phonology, g=k+voice, d=t+voice, b=p+voice and j=ch+voice so more comprehensive g,d,b and j has been assigned to ㄱ, ㄷ, ㅂ and ㅈ in order to differentiate them from ㅋ, ㅌ, ㅍ and ㅊ when the apostrophe is removed. And the environment in which ㄱ, ㄷ, ㅂ and ㅈ are pronounced as k,t,p and ch is articulated by the law.
For example, consonants ㄱ, ㄷ, ㅂ and ㅈ were decided to be romanized as k, t, p and ch when placed in the final position, as they are neutralized to unreleased stops: 벽[pjʌk̚] → byeok, 밖[pak̚] → bak, 부엌[pu.ʌk̚] → bueok, 벽에[pjʌ.ɡe̞] → byeoke, 밖에[pa.k͈e̞] → bakke, 부엌에[pu.ʌ.kʰe̞] → bueoke, 컵[k'ŏp] → keop.
ㅋ, ㅌ, ㅍ, ㅊ have been changed from k', t', p' and ch' to k, t, p and ch. (removing the apostrophe of the McCune–Reischauer system).
Vowels ŏ and ŭ are written as eo and eu, respectively (replacing the ŏ and ŭ of the McCune–Reischauer system).
However, ㅝ/wʌ/ is written as wo (not weo), and ㅢ/ɰi/ is written as ui (not eui)
ㅅ used to be written as sh and s, depending on context. Now it will be written as s in all cases.
ㅅ/s/ is written as s regardless of the following vowels and semivowels; there is no sh: 사[sa] → sa, 시[ɕi] → si.
When followed by another consonant or when in final position, it is written as t: 옷[ot̚] → ot (but 옷에[o.se̞] → ose).
ㄹ/l/ is r before a vowel or a semivowel and l everywhere else: 리을[ɾi.ɯl] → rieul, 철원[tɕʰʌ.ɾwʌn] → Cheorwon, 울릉도[ul.lɯŋ.do] → Ulleungdo, 발해[pal.ɦɛ̝] → Balhae. Like in McCune–Reischauer, ㄴ/n/ is written l whenever pronounced as a lateral rather than as a nasal consonant: 전라북도[tɕʌl.la.buk̚.do] → Jeollabuk-do
In addition, special provisions are for regular phonological rules in exceptions to transliteration (see Korean phonology).
Other rules and recommendations include the following:
A hyphen optionally disambiguates syllables: 가을 → ga-eul (fall; autumn) versus 개울 → gae-ul (stream). However, few official publications make use of this provision since actual instances of ambiguity among names are rare.
A hyphen must be used in linguistic transliterations to denote syllable-initial ㅇ except at the beginning of a word: 없었습니다 → eops-eoss-seumnida, 외국어 → oegug-eo, 애오개 → Ae-ogae
It is permitted to hyphenate syllables in the given name, following common practice. Certain phonological changes, ordinarily indicated in other contexts, are ignored in names, for better disambiguating between names: 강홍립 → Gang Hongrip or Gang Hong-rip (not *Hongnip), 한복남 → Han Boknam or Han Bok-nam (not *Bongnam or "Bong-nam")
Administrative units (such as the do) are hyphenated from the placename proper: 강원도 → Gangwon-do
One may omit terms such as 시, 군, 읍: 평창군 → Pyeongchang-gun or Pyeongchang, 평창읍 → Pyeongchang-eup or Pyeongchang.
However, names for geographic features and artificial structures are not hyphenated: 설악산 → Seoraksan, 해인사 → Haeinsa