The proper name for the episcopal headwear in question is zucchetto or pileolus, and is worn as an outward sign of the office held by the man wearing it. Papal zucchettos are white; cardinalate zucchettos are red, and episcopal zucchettos are violet. Although common in past centuries, in our culture and times, clothing rarely denotes rank, although fragments of the older tradition does remain in the military and in civil service positions that retain military traditions (e.g., civilian police, firefighters). So, for example, just as a military officer may wear gold braid on his shoulder to denote his rank, so a bishop wears a zucchetto to denote his rank.
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