Work, employment, occupation, calling, pursuit, business can all denote the specific kind of labor or activity in which a person engages seriously especially as a means of earning a livelihood.
Work is the most general of these terms; it applies to any kind of labor, whether physical or intellectual, whether carried on by the hour, day, week, month, or longer period, and whether done for pay or not and, if the former, whether compensated for by an employer or out of fees for services or the profits of a business.
Employment implies work for which one has been engaged and is being paid by an employer.
Occupation , though often used interchangeably with employment , can be more inclusive, for it does not necessarily connote service under an employer and may be referred to the work of a kind in which one engages habitually or for which one has been trained; thus, one seeks employment but follows a particular occupation .
Calling is sometimes used in place of occupation but is typically used of occupations which can be described as vocations or professions and to which one is likely to have been called by one’s nature or special tastes.
Pursuit , too, may be used in place of occupation but more specifically in the sense of a trade, craft, profession, business, or art that is followed often as a means of earning one’s living.
Business is often used in the sense of work or sometimes of occupation .