coastguard vs armed service

coastguard and armed service both are nouns.

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

As nouns, armed service is a hypernym of coastguard; that is, armed service is a word with a broader meaning than coastguard:

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

Other hypernyms of coastguard include military service, service.

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