Richard Stallman strongly advocates against lumping the three terms to mean “intellectual property”.
Copyright law was designed to promote authorship and art, and covers the details of expression of a work. Patent law was intended to promote the publication of useful ideas, at the price of giving the one who publishes an idea a temporary monopoly over it—a price that may be worth paying in some fields and not in others.
Trademark law, by contrast, was not intended to promote any particular way of acting, but simply to enable buyers to know what they are buying. Legislators under the influence of the term “intellectual property”, however, have turned it into a scheme that provides incentives for advertising.