A tide with one high water and one low water in a tidal day. See also: Semidiurnal tide

A type of tide having only one high water and one low water during a tidal day. The predominating type of tide throughout the world is semidiurnal, which has two nearly equal high waters and two nearly equal low waters in a tidal day. The third type of tide is the mixed tide, where there is an appreciable difference between the two high waters and between the two low waters; this difference is called diurnal inequality.

a tidal cycle where there is one high tide and one low tide in one lunar day (lunar day = 24 hours, 50 minutes).