rag week vs hebdomad

rag week and hebdomad both are nouns.

Word	Noun	Adjective	Verb	Adverb
rag week	Yes	No	No	No
hebdomad	Yes	No	No	No

As nouns, hebdomad is a hypernym of rag week; that is, hebdomad is a word with a broader meaning than rag week:

rag week: a week at British universities during which side-shows and processions of floats are organized to raise money for charities
hebdomad: any period of seven consecutive days

Other hypernyms of rag week include week.

rag week (noun)	hebdomad (noun)
a week at British universities during which side-shows and processions of floats are organized to raise money for charities	any period of seven consecutive days