behalf vs lieu

behalf and lieu both are nouns.

Word	Noun	Adjective	Verb	Adverb
behalf	Yes	No	No	No
lieu	Yes	No	No	No

As nouns, lieu is a hypernym of behalf; that is, lieu is a word with a broader meaning than behalf:

behalf: as the agent of or on someone's part (usually expressed as `on behalf of' rather than `in behalf of')
lieu: the post or function properly or customarily occupied or served by another

Other hypernyms of behalf include place, position, stead.

behalf (noun)	lieu (noun)
as the agent of or on someone's part (usually expressed as `on behalf of' rather than `in behalf of')	the post or function properly or customarily occupied or served by another
for someone's benefit (usually expressed as `in behalf' rather than `on behalf' and usually with a possessive)