noun
Deep emotional pain, sadness, or distress; often literary or formal. 愁い is especially associated with this nuance.
彼の顔には深い憂いの色が浮かんでいた。
A look of deep sorrow was on his face.
愁いを帯
The melody tinged with melancholy touched my heart.
noun
Worry about the future, unease, or misgivings; 憂い is the typical kanji for this sense.
将来への憂いが募る。
Anxiety about the future grows.
彼は国の行く末を憂いている。
He is worried about the future of the country.
Derived from the verb 憂う (うれう), meaning to worry or grieve. The kanji 憂, 愁, and 患 share overlapping meanings related to worry, sorrow, and illness, but 憂い is the most general written form.