A prothyrum (Romanization of Greek próthyron 'in front of the door'), in classical and medieval architecture, is a small porch, vestibule, or covered space immediately in front of the main doorway of a building. In architecture of the Greco-Roman world it was the transitional, often columned, space before the entrance proper. In the Late Antique and Byzantine periods, it could be a forecourt or portico preceding the narthex of a church or the main gateway of a monastic or palatial ensemble.
The Greek noun (próthyron) literally means âÂÂthe space before the doorâÂÂ. It can be spelled prothyron or the Latinized prothyrum in late Republican and Imperial texts.
In a narrow sense, a prothyrum is a shallow, often roofed architectural element marking and protecting the principal entrance. It could be formed by:
In Roman domestic architecture, authors distinguish between the vestibulum facing the street and the prothyrum that could articulate the immediate threshold zone before the atrium. In Late Antique and Byzantine religious architecture the word is sometimes used for the porch or foreâÂÂnarthex preceding the church proper, or for the covered space before a ceremonial gateway of a palace or monastery.
In medieval Latin texts from Southern Italy and the Byzantine Commonwealth the term (or its Greek equivalent) survives to denote porches attached to churches and fortified gatehouses. Early modern antiquarians, following classical dictionaries, reintroduced the latinised form in architectural glossaries, where it largely overlaps with the broader English words porch and vestibule.