Table: Primary Tidal Components
Table 1 gives the period and relative size of each of these constituents. While in some isolated situations, where other constituents become important, it is seldom essential to include many more to obtain accurate tidal predictions. In shallow water, the so-called compound tides generated by nonlinear interaction of primary constituents become important. For example, M4, generated by nonlinear self interaction of the M2 constituent has half the period of M2.