Fantasma vs. spettro
The Italian words 'fantasma' and 'spettro' both refer to supernatural entities, but they have subtle differences in usage and connotation.
Fantasma
'Fantasma' is the more common and general term for ghost or spirit. It often implies a visible apparition or the concept of a deceased person's soul.
Il castello è infestato da fantasmi.
(The castle is haunted by ghosts.)
Da bambino, avevo paura dei fantasmi sotto il letto.
(As a child, I was afraid of ghosts under the bed.)
Il fantasma di suo nonno gli apparve in sogno.
(His grandfather's ghost appeared to him in a dream.)
Spettro
'Spettro' is often used for a more frightening or menacing apparition. It can also refer to a specter or wraith, implying a less defined or more ethereal presence.
Lo spettro della guerra incombeva sulla nazione.
(The specter of war loomed over the nation.)
Vide uno spettro aggirarsi nel cimitero al crepuscolo.
(He saw a specter wandering in the cemetery at twilight.)
Gli spettri del passato continuavano a tormentarlo.
(The specters of the past continued to haunt him.)
Summary
While 'fantasma' is the more general term for ghost, often used in everyday contexts, 'spettro' tends to convey a more ominous or abstract presence. 'Fantasma' is commonly used for traditional ghost stories or folklore, while 'spettro' might be preferred in more literary or metaphorical contexts.