Teachers spend a lot of time encouraging students to use dictionaries properly. A good dictionary is an invaluable tool, containing essential information well-laid out, while a bad one badly-used will be a crutch at best, and a baffling thicket at worst.
I now only rarely see students using actual paper dictionaries. I toss them on to the table in classrooms pretty regularly, but most students have electronic devices of one sort or another, dedicated machines or on their phones or tablets. Some of these no doubt are very good, most are probably acceptable, but the sight of them for some reason makes me feel uneasy, not unlike the idea of ‘researching’ something on the Internet. The provenance of information – where it comes from – is key, more important than the information itself, but increasingly information has no provenance, it merely appears at the top of a Google search.
Anyway, dictionaries. It seems that the way the brain stores its lexicon may have a lot in common with dictionaries. Statistical analyses of dictionaries and the way the words in them are defined reveal a distinct nested hierarchy in operation. Only 10% of the words in a dictionary are used to define the rest of the words; and 5% of those key words can also be still be defined in terms of other key words; which means that a mere 5%, known as the Minimal Grounding Set, lie at the bottom of the dictionary, informing every other word (the actual words in this set vary from dictionary to dictionary).
This 5% of crucial core words are divided roughly equally between abstract and concrete meanings, suggesting that both are crucial to a full range of understand, but the abstract words congregate in so-called satellite groups of subject-specific reference, fully-related within but not outside the satellite.
As you move from full dictionary to kernel (10%) and then Minimal Grounding Set (5%), the words seem to be picked up by children at a younger and younger age, to be more frequently used, and to refer to more concrete concepts, suggesting that at root, our brains may be structuring and storing languages in in a complex but hierarchical manner, not unlike that of the dictionary.
So there you have it. The dictionary is a mirror of your mind, a sort of exo-brain, there on the desk. No wonder they are so useful.
For a more detailed explanation, read this New Scientist article.