Krafft-Ebing, like his contemporaries, even makes the point to exclude behavior front the diagnosis of homosexuality. These two phenomena must not be confounded with each other. More recent definitions often include both components. At the other extreme from the early definitions provided by Mayne and Benkert are definitions that only include discussions of the behavioral component. Here the psychological component does not seem to hold much if any importance for the assessment of sexual orientation.
Homosexuality refers exclusively to overt behavior between two individuals of the same sex.
Thus far I have discussed the two definitional components of sexual orientation as if the components themselves were uniform across definitions, but as is evident in the examples already provided, there are important variations. Each of these terms may have a distinct meaning and not necessarily be indicative of the same phenomenon. That is, different terms in definitions may be describing slightly different phenomena despite the similar label for that phenomena. Similarly, the behavioral component varies between definitions. Each one of these presents further challenges for researchers.