Zoidion is the original name for a “sign” of the zodiac in Greek.
Zōidion (ζῴδιον) is the singular, meaning “sign”, and zōidia (ζῴδια) is the plural, meaning “signs”.
Robert Schmidt has recently introduced the convention of translating zōidion as “image” in his translations of Hellenistic astrological texts, in order to better convey the original meaning underlying the Greek term.
Most translators simply translate zōidion as “sign”, in keeping with modern astrological conventions.
The English term “sign” is derived from the Latin word “signum”, which itself was used as a translation of zōidion in the Roman period.