office vs line of work

office and line of work both are nouns.

Word	Noun	Adjective	Verb	Adverb
office	Yes	No	No	No
line of work	Yes	No	No	No

As nouns, line of work is a hypernym of office; that is, line of work is a word with a broader meaning than office:

Other hypernyms of office include business, job, line, occupation.

office (noun)	line of work (noun)
a religious rite or service prescribed by ecclesiastical authorities	the principal activity in your life that you do to earn money
the actions and activities assigned to or required or expected of a person or group
a job in an organization
place of business where professional or clerical duties are performed
professional or clerical workers in an office
an administrative unit of government
(of a government or government official) holding an office means being in power