tristitiae
tristitiae is a Latin form of tristitia, meaning “sadness, sorrow; sternness”. It is the genitive singular feminine noun.
Found 40 times in the Latin texts on Socratos.
Where it is used
Cicero, Letters to his Friends 5.14.2: sin autem, sicut hinc discesseras, lacrimis ac tristitiae te tradidisti, doleo, quia doles et angere, non possum te non, si concedis, quod sentimus, ut liberius dicamu …
All forms of tristitia (declension table)
Source: Socratos (socratos.org), a free reader for Ancient Greek and Latin. Grammar from the Perseus Treebank and Morpheus; dictionary entries from Lewis & Short, A Latin Dictionary (Perseus Digital Library, CC BY-SA). Counts are from the texts on Socratos.