pipe vs briar

pipe and briar both are nouns.

Word	Noun	Adjective	Verb	Adverb
pipe	Yes	No	Yes	No
briar	Yes	No	No	No

As nouns, briar is a hyponym of pipe; that is, briar is a word with a more specific, narrower meaning than pipe:

pipe (noun)	briar (noun)
a long tube made of metal or plastic that is used to carry water or oil or gas etc.	a pipe made from the root (briarroot) of the tree heath
a tube with a small bowl at one end; used for smoking tobacco	evergreen treelike Mediterranean shrub having fragrant white flowers in large terminal panicles and hard woody roots used to make tobacco pipes
the flues and stops on a pipe organ	a very prickly woody vine of the eastern United States growing in tangled masses having tough round stems with shiny leathery leaves and small greenish flowers followed by clusters of inedible shiny black berries
a tubular wind instrument	Eurasian rose with prickly stems and fragrant leaves and bright pink flowers followed by scarlet hips
a hollow cylindrical shape