On thesaurus.com, you can filter synonyms by their "complexity." Does anyone know the criteria they use to determine a word's complexity?
After a little bit of testing I've noticed a couple things.
- The most complex words seem not to be labeled as common.
- The number of words making up a synonym increase as complexity increases
- The word length increases as complexity increases.
So it looks like its a weighted combination of those 3 factors. You'd have to try it out against a set of words and their corresponding complexity level sets to get at the exact algorithm, and you might find out there is another factor or two involved (such as number of synonyms available, etc).