Hello Suhyun, You can use 'on' for any day or date so 'I'll see you on Monday' or 'I'll see you on the 21st (June) are both correct. Also 'I'll see you on Christmas Day.' We use 'at' + time/holidays 'I'll see you at 6' or I'll see you at New Year.' and finally we use 'in' + period of time. ..in December, in the 1970s, in 1993, in the summer. Incidentally we would say "See you later today', 'See you tomorrow/next week/next month/next year.' all without a preposition. Hope this helps Bob

You would use 'on' for days in a basic sense. See you on Monday See you on Tuesday See you on Friday When we specify WHICH specific day, you don't See you next Monday See you next Tuesday I saw him last Wednesday There are no prepositions before tomorrow, yesterday, today.

you can use in for months on for days at for hours and about ur example See you on tomorrow.", OR "see you tomorrow." the both are correct

Both "I'll start this work on Sunday" or "I'll start this work Sunday are okay. Typically on can be used for the different days, such as Monday, tuesday, wednesday etc.