pipefish vs seahorse

pipefish and seahorse both are nouns.

Word	Noun	Adjective	Verb	Adverb
pipefish	Yes	No	No	No
seahorse	Yes	No	No	No

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

pipefish: fish with long tubular snout and slim body covered with bony plates
seahorse: small fish with horse-like heads bent sharply downward and curled tails; swim in upright position

pipefish (noun)	seahorse (noun)
fish with long tubular snout and slim body covered with bony plates	small fish with horse-like heads bent sharply downward and curled tails; swim in upright position
	either of two large northern marine mammals having ivory tusks and tough hide over thick blubber