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[sem-ee-dahy-ur-nl, sem-ahy-] /ˌsɛm i daɪˈɜr nl, ˌsɛm aɪ-/
pertaining to, consisting of, or accomplished in half a day.
occurring every 12 hours or twice each day.
Origin of semidiurnal
1585-95; semi- + diurnal Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for semidiurnal
  • Most tides are semidiurnal, which means they take place twice a day.
  • The littoral cell features a semidiurnal tidal pattern, two high tides and two low tides of unequal height every day.
  • The zero-dimensional model consists of a well-mixed control volume subjected to a semidiurnal tide, with a cohesive sediment bed.
  • Even though total coliform has a day-night cycle, it shows a stronger relationship to the semidiurnal tidal cycle.
  • The predominant type of tide throughout the world is semidiurnal, with two high waters and two low waters each tidal day.
  • These tides are mixed semidiurnal, meaning that there are two unequal low and high tides each day.
British Dictionary definitions for semidiurnal


of or continuing during half a day
occurring every 12 hours
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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