Work is often said to be hard to define. A precise working definition may nevertheless be valuable for analytical purposes, such as discussing justice in the distribution of work or the future of work. This paper takes a conceptual engineering approach to the concept of ‘work’. It examines the most common features of definitions of work in the contemporary philosophy of work: pay, negation of leisure, effort, social contribution, necessity/instrumentality and production of a benefit/external good. Of these, it argues that (...) the latter two can be refined into two equally suitable, co-extensive working definitions: Work is activity that is instrumental and intermediary to satisfy needs and wants, and Work is activity that produces a benefit (or intermediary product to a benefit) external to the worker(s) doing the activity. These are useful working definitions by virtue of coming close to a core of ordinary language ‘work’, being easily adaptable for various purposes, and for tracking a central feature of the human condition of particular importance for the philosophy of work. (shrink)