-아서/어서는 제안과 함께 쓰이지 않는다 - 그리고 '가장 높은 존댓말'의 함정
Eunseo is working through an 어휘·문법 set built around a single situation: it is raining, and she wants to suggest sharing a taxi. The three options are:
- (A) 비가 와서 택시를 탈까요?
- (B) 비가 오는데 택시를 탈까요?
- (C) 비가 오지만 택시를 탈까요?
Her tutor tells her that one of the three is ungrammatical, that the other two are grammatical but differ in meaning, and that "natural" and "grammatical" are separate verdicts she must report separately. In the same practice set she must choose how to ask her professor whether he has eaten lunch:
- (ㄱ) 선생님, 점심 드셨어요?
- (ㄴ) 선생님, 점심 잡수셨어요?
- (ㄷ) 선생님, 점심을 먹었습니까?
Eunseo assumes (ㄴ) must be best because 잡수시다 is the most honorific verb, and that (ㄷ) must be wrong because it is not honorific enough - but she cannot say what is actually wrong with it, and she has been told that her reasoning needs to name the grammatical category, not the feeling.
1. Identify the ungrammatical option, name the rule it violates, and distinguish the two remaining options by meaning.
Read the worked answer
Ungrammatical: (A). The connective -아서/어서 marks cause or sequence and cannot be followed by a 청유형 (-(으)ㅂ시다) or 명령형 ending. 탈까요? is a suggestion, so the cause clause and the ending are in conflict - the sentence is not a stylistic choice, it is a construction error. This is one of the most reliably tested points in Korean grammar because it is invisible to meaning: the sentence translates perfectly and is still wrong.
(B) uses -는데, which presents the rain as background circumstance and then offers the suggestion on top of it. It is the natural choice for "it's raining - shall we take a taxi?"
(C) uses -지만, which marks genuine contrast: "although it is raining, shall we take a taxi?" That implies rain would normally argue against a taxi, which is the opposite of the real-world logic. Grammatical, semantically strange.
Report them separately as your tutor asked: (A) ungrammatical; (C) grammatical but incompatible with the intended reasoning; (B) both grammatical and appropriate.
2. Choose among (ㄱ), (ㄴ) and (ㄷ) for speaking to a professor, and explain why "the most honorific verb" is not the selection criterion.
Read the worked answer
Best choice: (ㄱ) 선생님, 점심 드셨어요?
(ㄷ) is the informative error. -ㅂ니까 is a formal ending, but formality is not honorification: 먹었습니까 has no honorific marking on the verb at all, so it addresses the professor with formal grammar while failing to raise the subject. Korean requires both dimensions - the ending sets the register, and the verb form (드시다, 계시다, 주무시다) honours the subject. (ㄷ) gets one of two and is therefore wrong despite sounding stiff and polite to a learner's ear.
(ㄴ) is grammatically impeccable but 잡수시다 carries a strong, somewhat traditional flavour; 진지 잡수셨어요? is what a grandchild says to a grandparent, and using it with a professor can sound theatrical rather than respectful. (ㄱ) pairs the standard honorific 드시다 with 해요체, which is the normal register for a student addressing a professor in a friendly academic setting.
The criterion is not maximum honorific intensity but fit: subject honorific + appropriate register + the relationship. Overshooting is a real error in Korean, and it is the one this item is built to catch.