"(으)시" by itself is not an ending form, so I am not exactly sure what you are getting at. My guess is you might be confused between 하시다 and 하십니다 for example. There are many different endings and connective forms in Korean, which makes it difficult to learn. Grammar books will explain them, but I'll show a most basic summary of the endings. For the word "하다"(do), for example, there are four basic endings for the present tense. Closely related to "하다", there is another word "하시다", its "honorific" version - same meaning except it has a respectful connotation. Including both, there are eight basic ending forms. 하다 (root) - plain word for "do" (present tense ending forms of "하다") 합니다 (formal / polite ending) 한다 (formal / casual ending) 해요 (informal / polite ending) 해 (informal / casual ending) 하시다 (root) - honorific word for "do" to be used for elders and superiors. (present tense ending forms of 하시다) 하십니다 (formal / polite) 하신다 (formal / casual) 하셔요, 하세요 (informal / polite) 하셔, 해 (informal / casual) So you should get familiar with the dichotomy of words - the formality and politeness permutation makes for four versions for any given word. And then there is an honorific version of the word which brings its own four versions. Altogether, there are eight versions just for the plain basic endings in the present tense.

Let me complete Tony's explanation. ^-^ You cannot use -(으)시- when speaking about yourself. 저는 이미 결혼하셨어요. X 사장님은 이미 결혼하셨어요. O 저는 이미 결혼했습니다. O 사장님은 이미 결혼했습니다. O 저는 이미 결혼하셨습니다. X 사장님은 이미 결혼하셨습니다. O So you put the suffix -(으)시- when the subject of the verb is someone you show respect to. ㅂ/습니다 on the other hand, can be used whoever the subject is, you're just showing respect to the listener.

The endings used in a predicate can be divided into two classes. They are the connective endings and word final endings. The connective endings function as conjunctions in English, whereas word final endings are only used for closing a sentence. For examples, 가다, 가-고, 가-니, 가-(아)서, 가-지만, 가-면 The word final endings are divided into two types, pre-final endings and sentence final endings. conjugation: verb stem + pre-final endings + final ending The pre-final endings include : honorific for the agent of verb: -(으)시-, past tense : -았-/-었-/-였- humbleness for the speaker: -(사)옵- And the sentence final endings can be classified by seven speech levels according to the hearer/listener honorific system, 해라체, 해체, 해요체, 하게체, 하오체, 하십시오체, and 하소서체 , and by the sentence types such as declarative, interrogative, imperative, propositive, and exclamative. The honorific ending -시- changes normal verbs into honorific forms. This is used for only the agent of verb. Whereas the hearer honorific system are used for only who is spoken to, So, you should not confuse between these two methods. For examples, verb: 가다 honorific form: 가-시-다 The followings are the past tense declarative form of verb 가다/가시다 according to speech levels 해라체: 갔다/가시었다 해체 : 갔어/가시었어 해요체 : 갔어요/가시었어요 하게체 : 갔네/가시었네 하오체 : 갔소/가시었소 하십시오체 : 갔습니다/가시었습니다 하소서체 : 갔사옵나이다/가시었사옵나이다 The endings '-ㅂ니다' and '-습니다' in 하십시오체 are derived from '-옵-나이다' and '-사옵-나이다' in 하소서체. In other word, the letter 'ㅂ/습' in 'ㅂ니다/습니다' can be thought to a kind of clitic for pre-final ending '-옵-/-사옵-'.

(으)시 isn't an ending. It's an honorific particle. (스)ㅂ니다 is an ending. It's formal. (으)시 shows respect for the subject (whoever you're talking about). Therefore, it cannot be used to talk about yourself. (스)ㅂ니다 shows respect to the listener (whoever you're talking to). It is often used in the news. You can combine them therefore: 하십니다 하다: 해요 - informal polite (polite to listener) 하세요 - informal polite, honorific (polite to listener, respectful to subject) 합니다 - formal polite (more polite to listener) 하십니다 - formal polite, honorific (more polite to listener, respectful to subject)