is that pyx is the small container used to hold the consecrated bread of the eucharist while ciborium is a fixed vaulted canopy over a christian altar, supported on four columns.
As nouns the difference between ciborium and baldacchin
is that ciborium is a fixed vaulted canopy over a christian altar, supported on four columns while baldacchin is a rich, embroidered brocade used for clothing in the middle ages, the web being gold and the woof silk.
As nouns the difference between holding and ciborium
is that holding is something that one owns, especially stocks and bonds while ciborium is a fixed vaulted canopy over a christian altar, supported on four columns.