do i need both tourist visa & transit visa for india? confusing?

[Liam]

i m a US citizen travelling to kathmandu nepal via delhi. However i have 15 hrs transit/layover in delhi airport, so i would like to go out of airport to my friends home to spent night & return next day to continue my trip. the catch is I also want to visit india(delhi) after spending couple of weeks in nepal. So my question i guess is do i need both indian transit visa(to spend night out of airport) and also tourist visa to re-enter india? OR i just need Tourist visa which is multi-entry? appreciate your help!!