The terms are used indiscriminately in such popular 'feelgood' books as Nancy Friday's "Jealousy", where the expression 'jealousy' applies to a broad range of passions, from envy to lust and greed. While this kind of usage blurs the boundaries between categories that are intellectually valuable and psychologically justifiable, such confusion is understandable in that historical explorations of the term indicate that these boundaries have long posed problems. Margot Grzywacz's fascinating etymological survey of the word in Romance and Germanic languages asserts, indeed, that the concept was one of those that proved to be the most difficult to express in language and was therefore among the last to find an unambiguous term. Classical Latin used "invidia", without strictly differentiating between envy and jealousy. It was not until the postclassical era that Latin borrowed the late and poetic Greek word "zelotypia" and the associated adjective "zelosus". It is from this adjective that are derived French "jaloux", Provençal "gelos", Italian "geloso", and Spanish "celoso".