holiday [holidays](day on which a festival, religious event, or national celebration is traditionally observed) noun [UK: ˈhɒl.ə.deɪ] [US: ˈhɑːl.ə.deɪ]
observance [observances](the custom of celebrating a holiday) noun [UK: əb.ˈzɜː.vəns] [US: əb.ˈzɝː.vəns]