baldachin
Synonym discussion
Sense: noun/1
'Canopy' is the broad everyday word for any cover above a bed, door, stage, or person. 'Baldachin' is much rarer and more formal. It usually suggests a rich ceremonial cover connected with royalty or religion, and it can also extend to the fixed structure above an altar. 'Ciborium' is the more exact church-architecture term for that altar structure, especially when it stands on columns. 'Tester' is mainly used for the canopy over a bed or a throne. If you are describing ordinary shade outside a shop, use 'canopy'. Use 'baldachin' when the cover carries historical, sacred, or ceremonial importance.
Etymology
The word comes from Italian 'baldacchino', which first meant a rich silk cloth from Baghdad. Because ceremonial covers were often made from that fabric, English later used 'baldachin' for the cloth itself and then for the canopy or altar structure made from it.