IPA: /ˌsɛrəˈmoʊniəs/
KK: /sɛrəˈmoʊniəs/
Describing something that is formal and follows specific rituals or customs, often in a very serious or respectful way.
The wedding was a ceremonious event, filled with traditional rituals and formal attire.
Ceremonious is formed from "ceremony" (from Latin *caerimonia*, meaning a religious or formal observance) and the suffix "-ous" (meaning full of or characterized by). The word describes someone or something that is full of ceremony or marked by formal observance.
Think of 'ceremony' as a formal event, and remember that 'ceremonious' means full of ceremony or characterized by formality.