noun, noun which may take the genitive case particle 'no'
final stage; terminal stage
Used in medical contexts for terminal illness, as well as more broadly for the last phase of a process or life.
彼は終末期の患者に寄り添う医師だ。
He is a doctor who stays close to terminal patients.
このプロジェクトは終末期に入った。
This project has entered its final stage.