shore leave vs leave of absence

shore leave and leave of absence both are nouns.

Word	Noun	Adjective	Verb	Adverb
shore leave	Yes	No	No	No
leave of absence	Yes	No	No	No

As nouns, leave of absence is a hypernym of shore leave; that is, leave of absence is a word with a broader meaning than shore leave:

shore leave: leave granted to a sailor or naval officer
leave of absence: the period of time during which you are absent from work or duty

Other hypernyms of shore leave include leave.

shore leave (noun)	leave of absence (noun)
leave granted to a sailor or naval officer	the period of time during which you are absent from work or duty