English, with its overwhelmingly large vocabulary, presents problems not only for language learners but for native speakers as well. A report this morning on the BBC World Service illustrated the problem when a reporter misused the word interior instead of internal. These two words are not only close synonyms but are morphologically closely related. In speaking of the shooting in Kuala Lumpur of a Hamas operative, the reporter referred the event to “an interior matter” instead of “an internal matter” of the organization.
Such episodic mistakes, even by native speakers, are not rare, and normally the speaker making such an error immediately corrects it, typically by saying something like “I mean/meant” and supplying the correct word. Errare humanum est.