Domains are all equally unique — but they differ widely in their usability.
The most fundamental human information technology is natural language. As far as I know, there is no branch of knowledge (or “science” or whatever) that does not require natural language in order for humans to understand it. This may be slightly overstated, but not by much. I will leave the explanation of this little tidbit of “common knowledge” as an exercise for the reader.
In any case, humans (and probably many other life forms, too) need natural languages in order to communicate ideas (to each other).
In this vein, it is an easy, simple and straightforward observation to realize that natural language terms tend to be among the most usable domain names.
PHLAT design 