IPA: //ˌbɪtəˈswitnəs//
KK: /ˈbɪtərˌswitnəs/
The feeling or experience that is both happy and sad at the same time.
The bittersweetness of her graduation made her both proud and nostalgic.
Bittersweetness is formed from "bitter" (from Old English "bitter", meaning having a sharp taste or unpleasant flavor) and "sweet" (from Old English "swete", meaning having a pleasant taste). The suffix "-ness" (meaning the state or quality of) indicates the condition of being both bitter and sweet. Thus, bittersweetness refers to the quality of having both pleasant and painful emotions or experiences simultaneously.
Think of the contrasting flavors of 'bitter' and 'sweet' combined together, and remember that 'bittersweetness' describes the feeling of experiencing both joy and sorrow at the same time.
No commonly confused words.