지내세요 << 지내(다) + (으)시 + 어요 -> 지내시어요 -> 지내셔요 -> 지내세요. 지내다 means "to live" (으)시 is honorific addition 어요 is honorific ending suffix 지내요 << 지내(다) + 어요 -> 지내어요 -> 지내요. 지내다 means "to live" 어요 is honorific ending suffix You should add ‘~(으)시’ to verbs/adjectives in which the acting person deserves respect, regardless of who you are speaking to. You can add ‘~시’ to word stems ending in a vowel and ‘~으시’ to stems ending in a consonant. Once ‘~(으)시’ is added, the verb/adjective gets conjugated as usual as if the stem ended in ‘~(으)시.’ How are you doing?/ What's up? / What's new? 어떻게 지내세요? => used for the person who is elder person than the speaker 어떻게 지내요? => used for the person who is about the same age or younger than the speaker and is not intimate with the speaker.