contronyms

Contronyms, also known as auto-antonyms, contranyms, or Janus words, are words that contain opposite meanings, depending on the context. They are a form of lexical ambiguity in which a single term can express two opposing states or actions.

Common examples include: sanction (to permit; to penalize); cleave (to split apart; to adhere closely); dust (to remove dust; to apply dust); weather (to withstand; to wear away); oversight (supervision; an unintentional omission); left (having departed; remaining); fast (moving quickly; firmly fixed; to refrain from eating). These cases show how a word’s sense can flip with usage, tone, or surrounding words.

Origin and usage: Contronyms arise from semantic drift, polysemy, and layered historical meanings rather than deliberate opposition. They pose challenges for language learners and for automated systems, but context, syntax, and collocation usually resolve the intended sense. They are not true antonyms; rather, they are single forms that carry opposite meanings in different contexts, reflecting the dynamic and nuanced nature of language.