Wave, a ridge or swell on the surface of a body of water, normally having a forward motion distinct from the oscillatory motion of the particles that successively compose it. The undulations and oscillations may be chaotic and random, or they may be regular, with an identifiable wavelength between adjacent crests and with a definite frequency of oscillation. In the latter case the waves may be progressive, in which the crests and troughs appear to travel at a steady speed in a direction at right angles to themselves. Alternatively, they may be standing waves, in which there is no progression. In this case, there is no rise and fall at all in some places, the nodes, while elsewhere the surface rises to a crest and then falls to a trough at a regular frequency.
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