lousiness vs head lice

lousiness and head lice both are nouns.

Word	Noun	Adjective	Verb	Adverb
lousiness	Yes	No	No	No
head lice	Yes	No	No	No

As nouns, head lice is a hyponym of lousiness; that is, head lice is a word with a more specific, narrower meaning than lousiness:

lousiness: infestation with lice (Pediculus humanus) resulting in severe itching
head lice: infestation of the scalp with lice

Other hyponyms of lousiness include pediculosis capitis, pediculosis corporis, crabs, pediculosis pubis.

lousiness (noun)	head lice (noun)
the quality of being disgusting to the senses or emotions	infestation of the scalp with lice
infestation with lice (Pediculus humanus) resulting in severe itching