Non-philosophers are typically quite frustrated by the back-and-forth that results from theoretical definitions. To that end, some favor operational (or working) definitions, ones that work in practice to narrow down the range of phenomena under consideration.  This approach is often not considered a kind of definition by philosophers (see Gupta 2021). Operational definitions tend to be philosophically shallow. For example, NASA’s operational definition of life as “a self-sustaining chemical system capable of Darwinian evolution” (Joyce 1994) might include viruses while excluding mules. The lack of depth of an operational definition can frustrate theoretically minded people, including other scientists.