I guess I must be "the older generation". I would use the word "farewell" for final goodbyes. For example, if someone was leaving the country and not returning, I would say "farewell, old friend". The word is also used when someone is dying. For example, "the son went into the hospital room to say his final farewell to his father". Hope this helps

They are, technically speaking, synonyms. However, 'so long' and 'farewell' are not really used in English any more - at least as a greeting. You might say, "I am doing to someone's farewell-party.", meaning that you are going to the party where a group of people says farewell to someone. 'So long' is sometimes used, but you hardly hear it any more, unless amongst the older generation. We use lots of words: Ciao (Actually Italian)! Bye! See you later! Look after yourself. Be good. Don't do anything I wouldn't. Take care (British).....All these phrases are said when leaving another person. They obviously mean what they say, but you can use these phrases. Actually, 'bye' comes from Goodbye, which is a shortening for God Ye Bye - with the meaning of 'God be with you,' or 'God bless you.' But it no longer has that connotation or meaning.

'Farewell' is not used in casual spoken english anymore. It is considered archaic, overly formal and a bit pretentious. However, its meaning is exactly the same as goodbye. 'So long' is also not used very much. However, unlike 'Farewell' it isn't archaic, just not used often. If you did use it, which I don't suggest, it implies that you will not be seeing the person you are saying goodbye to for a significant about of time. "Goodbye' is used for any occasion when you are parting with someone. It can be used causally, formally, can be used if you will not see the person for a long time or even if you will see them very soon. If you want to be a bit more casual, or the goodbye won't be for long, you can just say 'Bye'.