1. 
   Semidiurnal
   Having a period or cycle of approximately one-half of a tidal day (12.4 hours). The predominating type of tide throughout the world is semidiurnal, with two high waterS and two low waters each tidal day. The tidal current is said to be semidiurnal when there are two flood and two EBB periods each da...
   Found op http://www.ecy.wa.gov/programs/sea/swces/products/glossary.htm
   
   
2. 
   Semidiurnal
   Sem`i·di·ur'nal adjective 1. Pertaining to, or accomplished in, half a day, or twelve hours; occurring twice every day. 2. Pertaining to, or traversed in, six hours, or in half the time between the rising and setting of a heavenly body;...
   Found op http://www.encyclo.co.uk/webster/S/63
   
   
3. 
   Semidiurnal
   • (a.) Pertaining to, or accomplished in, half a day, or twelve hours; occurring twice every day. • (a.) Pertaining to, or traversed in, six hours, or in half the time between the rising and setting of a heavenly body; as, a semidiurnal arc.
   Found op http://thinkexist.com/dictionary/meaning/semidiurnal/
   
   
4. 
   semidiurnal
   semidiurnal 1. In astronomy, pertaining to, consisting of, or performed in, half the time between the rising and setting of a celestial body; chiefly in semi-diurnal arc. 2. Occurring every twelve hours; primarily referring to the tides. 3. Pertaining to, or accomplished in, half a day, or twelve ...
   Found op http://www.wordinfo.info/words/index/info/view_unit/2459/2
   
   

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