It’s all about the nuance – synonyms and the Oxford English Corpus
There are few words that share an exact set of definitions – it is almost a guarantee that there will be some subtle differences between one word and its synonym. Sometimes these nuances are so subtle that they can be difficult to articulate fully in a definition, and only become apparent through examining usage.
Oxford Dictionaries rely heavily on the Oxford English Corpus, a collection of billions of words of English illustrating real use of the language; this enormous body of text illuminates changes that are occurring in the language, and also allows the distinctions between a word and its near-twin to be made clear.
Take, for instance, sustain and nourish. Two very similar words – close enough in meaning that each one is given as a synonym for the other in the thesaurus on the subscriber version of Oxford Dictionaries Online. Yet they each have other meanings and if we look at the way each is used in the Oxford English Corpus, some real differences become obvious.
The list of things that people typically sustain is not an enviable one – we often sustain injuries, damage, concussions, losses, and all manner of words that we would never think of as having anything to do with nourishment. We are far more likely to use nourish with such words as skin, spirituality, and embryo.
We sustain illusions, hope, or belief, and are more likely to nourish things like soil, souls, or earth. Does this mean that it would be incorrect to write that you ‘nourished illusions’ or ‘sustained the earth’? Not necessarily, although there is a decent chance that the phrase would sound awkward. One of the many advantages of a dictionary that is powered both by over a century of lexicographic knowledge and by over four billion words of use is that the changes and myriad subtleties in the language are sifted out and caught as they are happening – when usage changes, we can spot it.