bastion vs half-bastion

bastion and half-bastion both are nouns.

Word	Noun	Adjective	Verb	Adverb
bastion	Yes	No	No	No
half-bastion	Yes	No	No	No

As nouns, half-bastion is a hyponym of bastion; that is, half-bastion is a word with a more specific, narrower meaning than bastion:

bastion: projecting part of a rampart or other fortification
half-bastion: in military architecture, a bastion constructed of one face, and one flank.

bastion (noun)	half-bastion (noun)
projecting part of a rampart or other fortification	in military architecture, a bastion constructed of one face, and one flank.
a stronghold into which people could go for shelter during a battle
a group that defends a principle