I’d say that the distinguishing characteristic between the professional roles of
scientist and
engineer is mostly the expectation of your employer/investors/audience/etc. A scientist – or any of a wide variety of academics - is expected to produce research publications, which may or may not have practical application. An engineer is expected to produce artifacts – engines, bridges, computer hardware, software, scientific research equipment, etc.
Like nearly all titles, scientist and engineer are roles, defining some aspect of what a particular person does, not what they have, will, or can do. Many scientists undertake engineering challenges, and many engineers do basic science research. People with similar educational background may do either or both. These days, scientists frequently get involved in engineering companies, and engineering companies recruit scientists.
Another significant distinction among scientists/engineers, particularly in physics is
theoretician vs.
experimentalist. Given the quantity of specialized study and work involved, it’s difficult for a person who designs experiments for big particle accelerators to know enough engineering to actually build them, or a person who knows enough engineering to build them to keep up with theory well enough to know how to put them to good use.
Then there’s the distinction between mathematical physicists (Albert Einstein is a famous example of one) and mathematicians working in math interesting to physicists (
Hermann Minkowski is a famous example).