SECONDLY, there are six different styles of talking based on the SOCIAL considerations between THE SPEAKER and HEARER and the FORMALITY of the tones of the speaker to show the different levels of respectfulness. these styles are mainly concerned with differently conjugating the verbs of the sentences polite impolite formal 합쇼체 하오체 하게체 해라체 informal 해요체 해체 the degree of respectfulness 합쇼체> 해요체> 하오체> 하게체> 해체> 해라체

아니오 sounds formal, authoritative and outdated. we can see this word used in books and dramas with the backgraounds of old times as mentioned above and hear someone jokingly use this word to address someone below in terms of age and social rank acting as if the speaker were someone in a higher rung of the social hierachy. because 아니오 is a word from 하오체, (Hao style), one of many styles or tones of ending sentences to show respecfulness based on social extent and psycological distance and a person superior uses Hao style honorifics to talk to someone below with a dignified air. so a couple of years ago, with the growing popularity of korean historical hit dramas, Hao style was an in style to write comments on websites following the tones of the characters in the dramas with humour and fun. simply use this style (with fun intended if used these days) to talk to the hearer below in age and social rank with some respect in a dignified way as if a person of some sort of a title in old times of England would say with manners. 아니요 sounds informal, friendly, more psychologically close than 아니오, and is more frequently used these days than 아니오. we use 해요 style to talk to someone with some respect in a friendly way. but you had better not speak with this style in formal occasions such as a job interview, talking your old boss or high seniors in a meeting and talking to your future father-in-law for the first time and so on, depending on how koreans see the formality of social situations. so generally you can use this honorific style to talk to people nicely(meaning some repect---i feel sorry that i can't be more specific using the vague term 'some'^^) and informally(showing friendliness and psychological closeness to some extent) but you need to avoid this style and choose the highest fomal honorifics among the six other styles in the situations when fomality and seniority comes to your mind, having you more cautious in manners.

while we are at the korean honorific system, let's just go over it superficially (because that's all i can do with my smattering of korean grammer knowledge). there are two broad ways of showing repectfulness. FIRSTLY, based on subjects and objects within sentences, we have to add some appropriate postpositional words and verbs. for example, let's see the sentence "이것을 어머니께 갖다 드려라." (when a father tells a son to do that) in english, this turns into "bring this to your mother." becuse the mother is someone older than a son, deserving respect from the son and thusly honorifics. so first, right behind the word, mother, comes the honorific postpositional word, '께' instead of the normal postpositional word '에게' that is used to show that words such as persons, animals or things right in front of '에게' are an indirect object as an objective case among many(probably about 3) other usages of '에게'. second, because of the object 'mother' in the sentence, in harmony with '께' above, we need to choose the verb '갖다 드리다' showing repectfulness instead of the verb '갖다 주다' without respectfulness. let's break this sentance "이것을 어머니께 갖다드려라" with the element-by-element analysis. '이것' 'this' '을' the objective case indicating the direct object in the sentence ('을' here can be omitted in the sentence so it can be like '이것 어머니께 갖다 드려라') '어머니' 'mother' '께' the honorific form of '에게' that is the objective case indicating the indirect object in the sentence '갖다드려라' is made up of the transformed verb form '갖다드ㄹ' from '갖다 드리다', (the honorific verb meaning the word, 'bring') and 'ㅕ라' the ending conjugation of the 해라 style, the least respecful one that is used to order someone to do. so in short, one way of showing respecfulness in Korean is to use 'the RIGHT words' BASED ON THE SUBJECTS AND OBJECTS WITHIN THE SENTENCES.

Additionally, __오 is not used often nowadays. It sounds kinda antique because it's like King James words in English. We can only be heard on the historical things or Comedy shows.

Do you just copy and paste, 果報者? Just see the last word of the question, Silja. If it comes with 오, you can answer with 아니오. If it doesn't, then you can answer with 아니요(a honorific for 아니). If you'd love to know how those words go that way, feel free to contact me.