service door vs servant's entrance

service door and servant's entrance both are nouns.

Word	Noun	Adjective	Verb	Adverb
service door	Yes	No	No	No
servant's entrance	Yes	No	No	No

As nouns, service door and servant's entrance are synonyms defined as:

service door and servant's entrance: an entrance intended for the use of servants or for delivery of goods and removal of refuse

Other synonyms of service door include service entrance.

service door (noun)	servant's entrance (noun)
an entrance intended for the use of servants or for delivery of goods and removal of refuse	an entrance intended for the use of servants or for delivery of goods and removal of refuse