Melancholy

/ˈmɛlənkɑːli/ adjective medium

Filled with a thoughtful, lingering sadness.

A melancholy mood settled over the graduates as they said goodbye to classrooms they had known for four years.

Memory Trick

Ancient physicians blamed sadness on 'black bile' ('melan-' = black, '-choly' = bile) — melancholy still carries that old sense of a dark, heavy mood.