service vs coastguard

service and coastguard both are nouns.

Word	Noun	Adjective	Verb	Adverb
service	Yes	No	Yes	No
coastguard	Yes	No	No	No

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

service: a force that is a branch of the armed forces
coastguard: a military service responsible for the safety of maritime traffic in coastal waters

Other hyponyms of service include army, ground forces, regular army, naval forces, navy, Marines, air force, airforce.

service (noun)	coastguard (noun)
an act of help or assistance; something (such as a tool, software or system) used to render said help or assistance	a military service responsible for the safety of maritime traffic in coastal waters
the act of public worship following prescribed rules
(sports) a stroke that puts the ball in play
the act of mating by male animals
the act of delivering a writ or summons upon someone
periodic maintenance on a car or machine
the performance of duties by a waiter or servant
employment in or work for another
work done by one person or group that benefits another
(law) the acts performed by an English feudal tenant for the benefit of his lord which formed the consideration for the property granted to him
tableware consisting of a complete set of articles (silver or dishware) for use at table
a means of serving
a force that is a branch of the armed forces
a company or agency that performs a public service; subject to government regulation