occupation vs line of work

occupation and line of work both are nouns.

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

As nouns, occupation and line of work are synonyms defined as:

occupation and line of work: the principal activity in your life that you do to earn money

Other synonyms of occupation include business, job, line.

occupation (noun)	line of work (noun)
the principal activity in your life that you do to earn money	the principal activity in your life that you do to earn money
the act of occupying or taking possession of a building
the control of a country by military forces of a foreign power
any activity that occupies a person's attention
the period of time during which a place or position or nation is occupied