misreckon

From mis- +‎ reckon.

• (UK) IPA^(key): /mɪsˈɹɛkən/

misreckon (third-person singular simple present misreckons, present participle misreckoning, simple past and past participle misreckoned)

1. (transitive) To add (something) up incorrectly, make a wrong calculation of (an amount etc.).
2. (reflexive, obsolete) To make a wrong calculation, to be in error.
   • 1603, Michel de Montaigne, translated by John Florio, The Essayes […], London: […] Val[entine] Simmes for Edward Blount […], →OCLC:
     , Folio Society, 2006, vol.1, p.207:

     And therefore he that hath once misreckoned himselfe is never seene againe.

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