Starting from when I was a small child reading them on the living room floor, I've never fully grasped the reasons why an encyclopedia was not just a superset of the dictionary.
Me too :) But I think I have a better idea now.
An encyclopedia shouldn't be too language-specific. An ideal English encyclopedia and an ideal Icelandic encyclopedia could have approximately a one-to-one correspondance between articles. This would not at all be the case with an ideal pair of dictionaries.
Each language has its own arbitrary way of splitting the world up into words. For example Icelandic has a lot of more precise words for what English calls "tail".
dindill - sheep tail hali - cow tail tagl - horse tail rófa - dog tail stýri - cat tail skott - mouse tail stél - bird tail sporður - fish tail
When new things with tails come along they get one of these applied to them. Thus, an airplane has a "stél", a car has a "skott" and a smurf has a "dindill". There is no generic word in Icelandic for "tail".
But an encyclopedia tries to be somewhat independent of all this. It tries to split the world up into concepts that make sense from the point of view of our current state of knowledge. Those tails that have enough in common to be usefully described together should form one article, both in an English encyclopedia and an Icelandic one.
In practice I'm sure that the language an encyclopedia is written in will significantly impact its choice of entries.
Hmm... In this case [[tail]] is actually a dictionary entry masquerading as a disambiguation page.
Regards, Haukur