The Latent Structure of Dictionaries

Résumé 0

How many words – and which ones – are sufficient to define all other words? When dictionaries are analyzed as directed graphs with links from defining words to defined words, they turn out to have latent structure that has not previously been noticed. Recursively removing all those words that are reachable by definition but do not define any further words reduces the dictionary to a Kernel of 10%, but this is still not the smallest number of words that can define all the rest. About 75% of the Kernel is its Core, a strongly connected subset (with a definitional path to and from any word and any other word within it), but the Core cannot define all the rest of the dictionary. The 25% surrounding the Core are Satellites, small strongly connected subsets. The size of the smallest set of words that can define all the rest – a graph’s “minimum feedback vertex set” or MinSet – is about 1% of the dictionary, about 15% of the Kernel, about half-Core and half-Satellite, but every dictionary has a huge number of MinSets. The words in the Core turn out to be learned earlier, more frequent, and less concrete than the Satellites, which are learned earlier and more frequent but more concrete than the rest of the Dictionary. The findings are related to the symbol grounding problem and the mental lexicon.