How can the term "spirit" be translated into Buddhist doctrine?
It is citta (mind), which have cetasika (citta+nika;mind factors), such as feeling, emotions, etc. See more information in cittanupassanasatipatthana in mahasatipatthanasutta.

But if you mention to the ghost (citta+cetasikas+rupas), it is bhuta or sambhavesi in KN. Khuddakapatha ratanasutta &amp; it's atthakatha.

Abhidhamma describe this topic as tons.