The Korean language has a finite list of verbs and nouns that are used to refer to older or revered/esteemed people. These verbs and nouns are qualified as honorific, and must absolutely be used when talking to strangers and older people you know. The honorific verbs to be used when you speak to/talk about somebody esteemed are listed below. Do not use them to talk about your own actions/status. Make sure to check out the appropriate honorific nouns to use conjointly with these verbs (list forthcoming).
|만나다/보다||뵙다†||to meet/to see|
|아프다||편찮으시다||(to be) ill|
|있다||계시다***||to exist, to stay|
*말씀하다/말씀하시다: when you are talking to somebody esteemed to, for example, say "I will speak," do not say "말하겠습니다" but instead "말씀드리겠습니다." This is commonly heard when talking in front of a crowd. When you are talking about other people, use 말씀하시다, for example, "교수님께서 빨리 하라고 말씀하셨어요. (the professor said to do it fast)."
**드시다: can be used for both "to drink" and "to eat," but also for "to take a medication:" 약을 드시다 (약을 드세요) as honorifics for 약을 먹다 (약을 먹어요).
***계시다: used instead of 있다 to mean "to stay" and "to be/exist." For the meaning "to have," 있으시다 (있으세요) must be used instead of 계시다. For example, "교수님께서 교실에 계세요. (the professor is in the classroom)" vs "교수님께서 차가 있으세요 (the professor has a car)."
****드리다/주시다: 드리다 (드려요) is used when you are doing a favor/giving something to somebody esteemed, while 주시다 (주세요) is used when somebody esteemed is doing you a favor/giving you something. For example, if you are speaking to somebody esteemed, the two verbs have different meanings: "창문을 열어드릴게요. (I will open the window for you)" vs. "창문을 열어주세요. (please open the window)". Note that 드리다 replaces 주다 when 주다 is used as an auxiliary verb, such as in the previous example, but also when you are giving something to somebody esteemed; e.g., "할아버지께 사과를 드렸어요. (I gave an apple to my grandfather.)" vs. "친구한테 사과를 줬어요. (I gave an apple to my friend)." See more examples using 드리다.
†: these verbs are used when the object or recipient of the action is esteemed. Examples below:
(교수님께:) 내일 뵈겠습니다! (To the professor: see you tomorrow!)
"저는 부모님을 모시고 병원에 갔어요. (I took my parents to the hospital.)"
Compare with: "부모님께서 저를 데리고 병원에 가셨어요."
For a grammar reference book dealing with honorifics, I recommend Routlege's Korean: A Comprehensive Grammar, reviewed on KoniKorean. Section 4.4 (pp. 186-196) is all about honorific verbs and nouns, and how to use them according to a person's status.