-으시-

• 시 (-si-) — after vowels and ㄹ (l)
• 이시 (-isi-) — after stems that end in ㅅ (s), ㅈ (j), or ㅊ (ch)
• 우시 (-usi-) — after stems that end in the labial consonants ㅂ (b), ㅁ (m), & ㅍ (p)

Likely borrowed from Early Modern Korean 으시 (-usi-), and it is suggested that it may have come from exiled scholars and government officials from the mainland.[1][2] Ultimately from Old Korean 賜 (*-si).

• (Morphophonemic) IPA^(key): ⫽ɨsi⫽
• (Jeju City) IPA^(key): [ɨɕʰi]
• Phonetic hangul: [으시]

으시 (-eusi-)

1. An honorific suffix used primarily with the suffix 읍서 (-eupseo, “formal imperative suffix”) to show an increased level of deference or social distance.

   일름 ᄌᆞᆨ으십서. ― Illeum jawg-eusip-seo. ― Please write down your name.

   • 2020, Changyong Yang, Sejung Yang, William O'Grady, Jejueo: the language of Korea’s Jeju Island, Honolulu, USA: University of Hawai‘i Press, →DOI, →ISBN, →JSTOR, page 216:

     말 ᄀᆞᆯ으십서.

     Mal gawreusipseo.

     Please talk.

2. (rare) An honorific suffix for verbs and adjectives indicating that the subject of the sentence or the direct possessor of it is honored; it attaches directly to the stem, preceding all other suffixes.
   • 2020, Changyong Yang, Sejung Yang, William O'Grady, Jejueo: the language of Korea’s Jeju Island, Honolulu, USA: University of Hawai‘i Press, →DOI, →ISBN, →JSTOR, page 216:

     선싕님 오션.

     Seonsuing-nim o-syeon.

     The teacher arrived.

This ending is noted by multiple authors as a recent usage in the Jeju language, as it traditionally does have a complex system of subject honorifics like Korean does.[1][2][3][4]

• 시 (-si-) — after vowels and ㄹ (l)

From Middle Korean 으시〮/ᄋᆞ시〮 (Yale: -ùsí/òsí-), from Old Korean 賜 (*-si).

• (SK Standard/Seoul) IPA^(key): [ɯɕʰi]
• Phonetic hangul: [으시]

으시 • (-eusi-)

1. An honorific suffix for verbs and adjectives indicating that the subject of the sentence or the direct possessor of it is honored; it attaches directly to the stem, preceding all other suffixes.

   얘야, 형님은 운동을 언제 하시냐?

   Yae-ya, hyeongnim-eun undong-eul eonje hasinya?

   Child, when does your older brother do his exercises?

   손이 정말 예쁘시네요.

   Son-i jeongmal yeppeusineyo.

   Your hand is truly pretty.

   선생님께서 여기로 오신다.

   Seonsaengnim-kkeseo yeogi-ro osinda.

   The teacher is coming here.

2. (proscribed) An honorific suffix for verbs and adjectives indicating that the addressee (not the subject or the possessor) is honored

   손님, 문이 열리시겠습니다.

   Sonnim, mun-i yeollisigetseumnida.

   Sir, the door is about to open.

• Honoring may be considered a broad or confusing term, but it indicates that the speaker is implying that the subject (or the possessor of the subject) is above their social status level; this can include people from parents and siblings to chiefs of companies, professionals like doctors, and the president. It can also be used sarcastically, such as when joking with a close friend.
• Within the more older generation, the honorific suffix can be seen used to honor the weather such as 비가 오신다 (biga osinda, “it is raining”), this is becoming less and less common though.
• Traditionally, when a third person is honored, the speaker is implying that the addressee is also below the social status of the third person. As a result, this can come across as rude to the listener if the listener is not actually of such lower status. This use of the honorific is called 압존법 (apjonbeop). However, this principle is increasingly less used among younger speakers, who might instead often consider it impolite to not honor the third person.
• In the colloquial language, 시 (-si-) is also used to honor the addressee in a conversation to a level greater than that allowed by the 습니다 (-seumnida) suffix alone. Despite the fact that this is attested since as early as Middle Korean, this form is still generally considered prescriptively wrong, although it remains widespread and may eventually be accepted as standard.
• As the suffix begins with ㅅ (s), it causes the root ㄹ (l) to elide: 우시다 (usida, “for someone to cry”) from 울다 (ulda, “to cry”).
• Some verbs have special forms of honorifics that use a different root. These verbs include: 계시다 (gyesida), 잡수시다 (japsusida), 드시다 (deusida), etc...

• 님 (nim), the honorific suffix for many nouns
• 께서 (-kkeseo), the honorific nominative case suffix
• 옵 (-op-), the object honorific