**Science / Tides and Currents / Diurnal Inequality:** The difference in height of the two high waters or of the two low waters of each tidal day; also, the difference in speed between the two flood tidal currents or the two ebb currents of each tidal day. The difference changes with the declination of the Moon and, to a lesser extent, with the declination of the Sun. In general, the inequality tends to increase with increasing declination, either north or south, and to diminish as the Moon approaches the Equator. Mean diurnal high water inequality (DHQ) is one-half the average difference between the two high waters of each tidal day observed over the National Tidal Datum Epoch. It is obtained by subtracting the mean of all the high waters from the mean of the higher high waters. Mean diurnal low water inequality (DLQ) is one-half the average difference between the two low waters of each tidal day observed over the National Tidal Datum Epoch. It is obtained by subtracting the mean of the lower low waters from the mean of all the low waters. Tropic high water inequality (HWQ) is the average difference between the two high waters of each tidal day at the times of tropic tides. Tropic low water inequality (LWQ) is the average difference between the two low waters of each tidal day at the times of tropic tides. Mean and tropic inequalities, as defined above, are applicable only when the type of tide is either semidiurnal or mixed. Diurnal inequality is sometimes called declinational inequality.

**Diurnal Adjective Synonyms**: daily, circadian, day-to-day, regular, everyday, quotidian, daytime

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**Inequality Noun Synonyms**: disparity, difference, discrepancy, unevenness, nonconformity, incongruence, incongruity, inconsistency, dissimilarity, imbalance

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Science / Tides and Currents / Age Of Diurnal Inequality: The time interval between the maximum semimonthly north or south declination of the Moon and the maximum effect of declination upon range of tide or speed of the tidal current. The age may be computed MORE

Science / Tides and Currents / Inequality: A systematic departure from the mean value of a tidal quantity. See diurnal inequality, parallax inequality, and phase inequality. MORE

Science / Tides and Currents / Parallax Inequality: The variation in the range of tide or in the speed of a tidal current due to changes in the distance of the Moon from the Earth. The range of tide and speed of the current tend alternately to increase MORE