A 2-place word acts as a function of 2 arguments ("2-place function"). For example:
Sexiness: Admirer, Entity -> [0, ∞)
A 1-place word acts as a function of 1 argument ("1-place function"). For example:
Sexiness: Entity -> [0, ∞)
Treating a 2-place word as a 1-place word can result in silly mistakes like assuming that a bug-eyed monster would naturally want to carry off a girl in a torn dress. People think as if sexiness is an inherent property of a sexy entity, without dependence on the admirer.
"Of course the bug-eyed monster will prefer human females to its own kind," says the artist (who we'll call Fred); "it can see that human females have soft, pleasant skin instead of slimy scales. It may be an alien, but it's not stupid - why are you expecting it to make such a basic mistake about sexiness?"