"Good morning, dear!"
Translation:Bonan matenon, kara!
So whrn does one say Bone versus Bonan? Are they just entirely different words?
'Bone' is the adverb form ('well') and 'bona' is the the adjective form ('good'). 'Bonan' is the accusative (direct object) inflection of 'bona'. Phrases like 'good morning' or 'thanks' are actually short for sentences e.g. 'I hope you have a good morning' ('Mi esperas ke vi havas bonan matenon') or 'I give you thanks' ('Mi donas al vi dankon'), which is why you use the accusative case.