regalia
Concise Oxford English Dictionary © 2008 Oxford University Press:
regalia /rɪˈgeɪlɪə/
▶plural noun [treated as sing. or pl.]
- 1 the insignia of royalty, especially the crown and other ornaments used at a coronation.
- 2 the distinctive clothing and trappings of high office, worn at formal occasions.
– origin C16 (in the sense ‘royal powers’): from med. L., lit. ‘royal privileges’, neut. pl. of regalis ‘regal’.
usage: The word regalia comes from Latin and is, technically speaking, the plural of regalis. However, in modern English use it behaves as a collective noun, similar to words like staff or government, which means that it can be used with either a singular or plural verb.
'regalia' also found in these Oxford entries:

