send-off vs word of farewell

send-off and word of farewell both are nouns.

Word	Noun	Adjective	Verb	Adverb
send-off	Yes	No	No	No
word of farewell	Yes	No	No	No

As nouns, word of farewell is a hypernym of send-off; that is, word of farewell is a word with a broader meaning than send-off:

send-off: an organized expression of goodwill at the start of a trip or new venture
word of farewell: an acknowledgment or expression of goodwill at parting

Other hypernyms of send-off include farewell.

send-off (noun)	word of farewell (noun)
an organized expression of goodwill at the start of a trip or new venture	an acknowledgment or expression of goodwill at parting
a start given to contestants