devotion vs allegiance

devotion and allegiance both are nouns.

Word	Noun	Adjective	Verb	Adverb
devotion	Yes	No	No	No
allegiance	Yes	No	No	No

As nouns, allegiance is a hypernym of devotion; that is, allegiance is a word with a broader meaning than devotion:

devotion: commitment to some purpose
allegiance: the act of binding yourself (intellectually or emotionally) to a course of action

Other hypernyms of devotion include commitment, dedication, loyalty.

devotion (noun)	allegiance (noun)
(usually plural) religious observance or prayers (usually spoken silently)	the act of binding yourself (intellectually or emotionally) to a course of action
commitment to some purpose	the loyalty that citizens owe to their country (or subjects to their sovereign)
religious zeal; the willingness to serve God
feelings of ardent love